Respectful Insolence

Pertussis outbreaks and vaccine effectiveness

About a month ago, I deconstructed a typically dishonest and deceitful attempt by that Overlord of Quackery on the Internet (in my opinion, of course), Joe Mercola, to claim that the acellular pertussis vaccine doesn’t work. It was a typical Mercola bit of prestidigitation that, as so much antivaccine propaganda does, took a grain of truth (that there have been outbreaks among vaccinated populations) and ran with it to construct a fantasy world in which pertussis outbreaks are somehow an indictment of all vaccines, which, of course, don’t work at all, ever, under any circumstances, anywhere at least in the minds of antivaccinationists.

Perhaps the biggest difference between science-based doctors and quacks is a very simple one. When a treatment or preventative measure isn’t working as well as it should, we science-based physicians ask why. We try to find out what is not working optimally. We try to figure out how to make things better. So it is with the acellular pertussis vaccine. It’s no secret that recent outbreaks have been notable for a large contingent of vaccinated children being involved. Indeed, I cited two studies that both basically agreed that there appears to be a hole in the vaccination schedule that leaves children in the 10-12 year age range inadequately protected, such that the attack rate is nearly equal in vaccinated and unvaccinated or undervaccinated children during the outbreaks was nearly the same. Antivaccinationists love to cite these studies, but what they always leave out is the finding that the acellular pertussis vaccine is effective in protecting younger children and also in protecting teens who have received the recommended booster at age 11 or 12.

In other words, antivaccinationists willfully invoke the fallacy of the perfect solution (also known as the Nirvana fallacy), which I like to liken to an old sketch Mike Myers back when he was on Saturday Night Live in which he played a Scotsman who would loudly say, “If it’s not Scottish it’s crap.” Basically, under this fallacy, if a vaccine doesn’t work perfectly 100% of the time, it’s crap. If it isn’t absolutely, positively, 100% safe, it’s crap. If it fails, even just once, to protect against the disease it’s designed to protect against, it’s crap. Never mind that nothing in medicine is 100% effective and safe and the only certainty in medicine (and life) is that all of us will one day die.

None of this is to say that we shouldn’t strive to improve the acellular pertussis vaccine or improve the vaccine schedule, and that was the topic of a recent paper in the New England Journal of Medicine by Dr. James D. Cherry, a pediatrician at the David Geffen School of Medicine, University of California at Los Angeles, Los Angeles entitled Epidemic Pertussis in 2012 — The Resurgence of a Vaccine-Preventable Disease. He begins by noting that we are currently experiencing what may turn out to be the largest outbreak of pertussis in 50 years, asking the question: Why has this theoretically vaccine-preventable disease been on the upswing? Several answers are forthcoming, but here’s a graph of pertussis versus time:

It’s first noted that whooping cough is a cyclical disease. In the pre-vaccine era, there were epidemics every two to five years. Although vaccination was wildly successful in reducing the incidence from 157 per 100,000 in the 1940s to 1 per 100,000 in 1973, infection does not, contrary to the claims of antivaccinationists that “natural immunity” is permanent, produce lifelong immunity; neither does the vaccine. Cherry notes that this is in marked contrast to, for example, measles, for which immunity due to the vaccine is much longer. So now, even though there isn’t as high an incidence of whooping cough, the causative organism, Bordetella pertussis is still circulating in a manner similar to the way it did in the pre-vaccine era. Until recently, it just wasn’t causing epidemics the way that it did before.

Cherry tells us that there are actually two relevant issues to consider: The epidemiology of reported pertussis cases and the epidemiology of pertussis infection. He notes that existing studies suggest that 13 to 20% of prolonged coughs in adolescents and adults are likely due to B. pertussis infection, and studies examining antibody titers suggested an infection rate between 1% and 6%. In other words, there’s a lot of mildly symptomatic pertussis out there, which leads Cherry to ask:

So what are the causes of today’s high prevalence of pertussis? First, the timing of the initial resurgence of reported cases (see graph) suggests that the main reason for it was actually increased awareness. What with the media attention on vaccine safety in the 1970s and 1980s, the studies of DTaP vaccine in the 1980s, and the efficacy trials of the 1990s comparing DTP vaccines with DTaP vaccines, literally hundreds of articles about pertussis were published. Although this information largely escaped physicians who care for adults, some pediatricians, public health officials, and the public became more aware of pertussis, and reporting therefore improved.

Antivaccinationists will no doubt scoff at this suggestion the same way that they scoff at any suggestion that the increased prevalence of autism over the last 20 years could possibly be due to greater awareness and intensive screening programs, but as I’ve pointed out before, it’s a truism in medicine that whenever you look for a disease you will find more of it—sometimes a lot more, particularly if you use more sensitive tests or broaden the diagnostic criteria (the latter of which was done for autism in the early 1990s).

Even though I’ve used this example within the last six months, it bears repeating because it’s in my specialty and it illustrates the concept. Basically, the same sort of thing happened when mass mammography screening programs were undertaken with an entity called ductal carcinoma in situ (DCIS). This is a premalignant precursor of breast cancer, some proportion of which will progress to full-blown cancer. Basically, it’s cancerous cells that haven’t broken out of the breast ducts yet to invade the surrounding tissue. A few decades ago, DCIS was fairly rare because by the time it grew large enough to be a palpable mass, it almost always had become invasive cancer. Now, thirty years or so after mass mammographic screening programs began, DCIS is common. In fact, it’s the most common diagnosis of breast cancer made, making up approximately 40% of breast cancer diagnoses Once again, I’ll cite a recent study that reported that DCIS incidence rose from 1.87 per 100,000 in the mid-1970s to 32.5 in 2004. That’s a more than 16-fold increase over 30 years. There’s no reason to suspect that the “true” incidence of breast cancer is increasing. (Indeed, it’s not.) So that implies that this increase was pretty much all due to the introduction of mammographic screening. Other examples abound in medicine, including hypertension, hypercholesterolemia, and others.

Cherry suggests that one factor behind the rise in pertussis lately is similar:

Moreover, during the past decade, polymerase-chain-reaction (PCR) assays have begun to be used for diagnosis, and a major contributor to the difference in the reported sizes of the 2005 and 2010 epidemics in California may well have been the more widespread use of PCR in 2010. Indeed, when serologic tests that require only a single serum sample and use methods with good specificity become more routinely available, we will see a substantial increase in the diagnosis of cases in adults.

In other words, some of what’s going on here might just be overdiagnosis, in which mildly symptomatic cases or cases that aren’t that serious are picked up that once might have been dismissed as a persistent “crud.” Clearly, though, that’s not the only thing going on. Two other issues are likely also contributing. The first is the issue that I discussed before, namely waning immunity from the acellular pertussis vaccine. Cherry cites five studies showing that the old DTP (the whole cell pertussis vaccine combination with the tetanus and diphtheria vaccine) was more efficacious than the DTaP (the acellular pertussis vaccine combination), as well as the California studies whose misuse by Mercola I discussed before. One needs to remember that the switch from the DTP combination vaccine to the DTaP combination vaccine was largely due to concerns about the safety of the DTP back in the 1980s that led to the rise of Barbara Loe Fisher and her antivaccine group the National Vaccine Information Center (NVIC) over reports of encephalopathy after the vaccine, fears that later studies failed to confirm. So, in essence, we traded a highly effective vaccine for one that’s effective, but not quite as effective.

Finally, there’s this:

Finally, we should consider the potential contribution of genetic changes in circulating strains of B. pertussis.4 It is clear that genetic changes have occurred over time in three B. pertussis antigens — pertussis toxin, pertactin, and fimbriae. In fact, changes in fimbrial agglutinogens related to vaccine use were noted about 50 years ago. Studies in the Netherlands and Australia have suggested that genetic changes have led to vaccine failures, but many people question these findings. If genetic changes had increased the rates of vaccine failure, one would expect to see those effects first in Denmark, which has for the past 15 years used a vaccine with a single pertussis antigen (pertussis toxin toxoid). To date, however, there is no evidence of increased vaccine failure in Denmark.

These are the observations behind the claims by cranks like Mercola that vaccines are “causing dangerous mutations.” While it is possible that the B. pertussis bacteria is developing “resistance” to the vaccine through natural selection, the evidence that it is doing so strikes me as rather weak and preliminary. Even if it were, the answer would be to change the vaccine in order to include the altered antigens. After all, do we decide that antibiotics don’t work when bacteria evolve resistance or that chemotherapy doesn’t work when tumors manage to do the same? That’s a rhetorical question, of course. Some segments of the alt-med world do, but reasonable scientists do not. They work to overcome that resistance.

Leaving aside that hypothetical problem that might be contributing to pertussis epidemics in the era of the acellular vaccine, what can be done to bring these epidemics under control? Some of what Cherry mentions are the same things I mentioned the last time I discussed this issue. First, he notes that the purpose of vaccination against B. pertussis is not to eliminate all disease. It’s to prevent serious disease with its potentially horrific complications, up to and including death, particularly among young infants. One possible approach would be to start DTaP at a younger age with shorter intervals between doses. Another strategy is to immunize pregnant women in order to reduce the risk that the mother will acquire pertussis around the time of delivery, with the added bonus that it would give the infant some protection for a month or two through maternal antibodies.

The point of course is that these recent epidemics, while they point to problems with the current vaccination schedule, do not by any means demonstrate that the vaccine doesn’t work or that it’s failed.

I also have one final point. While the evidence that pockets of unvaccinated children are the nidus for measles outbreaks is very clear, these latest pertussis outbreaks do not appear to be strongly related to pockets of unvaccinated children. There’s no doubt that having pockets of unvaccinated children doesn’t help. They are, after all, at a 23-fold increased risk of catching whooping cough, which allows for the degradation of herd immunity at the very least as well as providing a reservoir for the offending bug, and even the latest studies out of California indicate that for most age ranges unvaccinated and undervaccinated children are at a significantly higher risk of catching pertussis than fully vaccinated children; the problem is primarily at one age range where waning immunity from the DTaP leaves a gap in immunity. However, in this case, as far as I’ve been able to tell, they do not appear to be the primary drivers of these most recent epidemics, as they are for measles outbreaks. We as science-based supporters of vaccination have to be careful not to overstate our case.

Would that antivaccinationists would do the same. Actually, would that antivaccinationists would actually stop spreading misinformation. The difference between science-based supporters of vaccination and antivaccinationists is simple. We face reality. Evidence and science matter to us. When vaccines do not function as well as we would like and try to fix it. As Cherry reminds us, even with these new epidemics, today’s incidence of pertussis is still about one twenty-third what it was during a typical epidemic year in the 1930s. Indeed, a reader sent me a link to a presentation by Thomas Clark, MD, MPH about pertussis epidemiology and vaccination. This slide set includes a slide that takes the slide above and puts it in context:

That rather puts the antivaccinationists’ attacks on the acellular pertussis vaccine into perspective, doesn’t it? Indeed, I can’t help but note that the graph above shows the total number of cases. Because the U.S. population has grown considerably over the last 90 years, if it were graphed by incidence, the effect of the vaccine would be even more striking. In any case, this graph illustrates quite clearly that the pertussis epidemics over the last few years are mere blips on the curve compared to what we saw in the past, before there was a vaccine available to combat pertussis. Still, although this is good, it is not nearly good enough. We can do better. Contrary to what antivaccinationists tell us, recent outbreaks of pertussis do not mean that vaccines don’t work. They mean that we need to use the vaccine we have better and possibly develop newer vaccines that overcome the shortcomings of the existing vaccine.

Comments

  1. #1 Darwy
    Røde grøde med fløde
    September 5, 2012

    I know the vaccine schedule in Denmark is different from the US: they don’t vaccinate against Hep A or B, for example.

    They also have a different timeframe for the MMR and DTaP – with the 2nd MMR dose at 4 years, and the DTaP at 5 years, where a lot in the US get it at 4 years (even though the range is 4-6).

    Might be part of the reason there’s no incidence of increased vaccine failure.

  2. #2 dingo199
    September 5, 2012

    Here is some of the evidence that natural immunity is only mildly longer lasting than vaccine acquired immunity.
    http://journals.lww.com/pidj/Fulltext/2005/05001/Duration_of_Immunity_Against_Pertussis_After.11.aspx

    Range for natural immunity is 4-20 years, for vaccine-induced immunity it is 4-12 years, with little tangible difference between wP and aP vaccination, though some observations suggest wP-induced immunity is more durable. The experience of differing vaccination schedules seems to have given rise to much of this evidence for duration of immunity.

  3. #3 dingo199
    September 5, 2012

    However, I should also point out that more recent epidemiological analysis suggests natural infection induces immunity that may be around 30 years on average, but which is very variable.
    http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1000647

  4. #4 elburto
    September 5, 2012

    Orac – I mentioned this in the anti-vaccine thread a few days ago, but here in the UK the Department of Health is considering vaccinating newborns against pertussis.

    From January to August we had three times as many cases* as in the whole of 2011, and babies have already died.

    http://www.bbc.co.uk/news/health-19454493

    *Mumps has quadrupled, I believe measles cases have doubled. These are confirmed cases only.

    Infectious disease data for the UK is here: http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/

  5. #5 Grant
    September 5, 2012

    dingo199,

    I recall reading somewhere that one way to reconcile these is for the actual ‘natural’ immunity to be quite short, but for some people to get sub-clinical infections that effectively act as boosters. (It might be the first of the two papers you cite, actually; haven’t time to revisit it to check – excuse me for that.)

  6. #6 Science Mom
    http://justthevax.blogspot.com/
    September 5, 2012

    I ran some numbers on the Washington state pertussis outbreak and unvaccinated/undervaccinated have higher attack rates:

    Attack rates for vaccinated (ARv) and un/der vaccinated (ARn) are as follows:

    Ages 5-9: (ARv) 500/411023 x 100 = 0.12%
    (ARn) 159/21633 x 100 = 0.73%

    Ages 10-13 (ARv) 356/329076 x 100 = 0.11%
    (ARn) 469/17320 x 100 = 2.7%

    Ages 14-18 (ARv) 477/431968 x 100 = 0.11%
    (ARn) 141/22735 x 100 = 0.62%

    As we can see, more un/undervaccinated children have been infected with pertussis than fully vaccinated across all age bins. This translates to children ages 5-9 un/der vaccinated children are 6 times more likely to become infected with pertussis than fully vaccinated. Children ages 10-13 un/der vaccinated are 25 times more likely to become infected with pertussis than fully vaccinated. And un/der vaccinated children ages 14-18 are 6 times more likely to become infected with pertussis than fully vaccinated.

    http://justthevax.blogspot.com/2012/08/washington-state-pertussis-outbreak.html

  7. #7 dingo199
    September 5, 2012

    Grant, that is probably very true, and is referred to in the PLOS article. It certainly applies for diseases like chickenpox and measles, where natural boosters keep immunity topped up.

    This bit of the PLOS paper was interesting:

    Accurate assessment of the duration of immunity after natural infection or vaccination is crucial for pertussis control, and yet our understanding of immunity to pertussis is limited. The central obstacle is that despite a great deal of clinical research, it remains impossible to correlate protection against pertussis with a quantifiable immune response against a single protective antigen [16]–[18]. This is partly because, in contrast to other vaccine-preventable bacterial infections, such as diphtheria or tetanus, where antibodies are known to protect against the toxin that mediates disease, pertussis produces a range of toxins including pertussis toxin, endotoxin, adenylate cyclase toxin and tracheal cytotoxin, which are known to play a role in pathogenesis and immune evasion [19]. Immunity to pertussis is further complicated by the production of numerous virulence factors (filamentous hemagglutinin, pertactin and fimbriae) that aid bacterial persistence in the respiratory tract. Moreover, in addition to binding to epithelial cells in the respiratory tract (which facilitates extracellular multiplication), pertussis also survives within macrophages and other cell types, an observation that argues for a role for cell-mediated as well as humoral immunity in protection [19],[20].

    Much of the pertussis work stems from the era predating widespread use of the acellular vaccine. Our concepts about vaccine-induced immunity will probably change to account for this.

    Also interesting is the idea that pertussis control is still an achievable goal through vaccination

    In turn, the implications of these observations are that (i) natural pertussis infection induces, on average, considerably long-lasting immunity, (ii) repeat infections contribute relatively little to the transmission cycle, and (iii) secondary exposures generate few infections (and may lead mostly to immune boosting). Taken together, these conclusions raise doubts over the impact of repeat infections in pertussis dynamics. If correct, these findings represent reasonably encouraging news for pertussis control, indicating that a reduction in prevalence (and an increase in the CCS) is possible with continued focus on increasing vaccine uptake and reducing both primary and secondary vaccine failure.

  8. #8 johnV
    September 5, 2012

    Sequencing is so cheap now, if people are hypothesizing “vaccine-driven” evolution it should be a trivial to sequence several historical strains, assuming some are in freezers that haven’t been passaged too many times, and modern epidemic strains from wherever.

    The genome is like 4mb, that means you can multiplex 4 or 5 strains per Illumina lane so like $3500 per 4 strains sequenced.

  9. #9 Passionlessdrone
    The corner of dude and catastrophe
    September 5, 2012

    Very nicely written article.

    The periodic nature of outbreaks leaves mlimited confused than usual. Does anyone have a proposed mechanism for why we observe three to five year surges in cases?

    – pD

  10. #10 Denice Walter
    September 5, 2012

    OT ( but it’s a dreary, grey day and I thought some of you might be entertained by the inverse of brilliance- which is NEVER OT @ RI)

    Mike Adams ( Natural News) informs us that the recent review ( Annals of Internal Medicine)- that compares organic and conventional foods and found no important health differences- is nothing but a “media psyop” ( his neologism).

    But, but, but, he sputters, they don’t consider GMOs, artificial sweeteners and growth hormones.

    Obviously this is but another example of media lies! Just like those told about vaccines!

  11. #11 Science Mom
    http://justthevax.blogspot.com/
    September 5, 2012

    The periodic nature of outbreaks leaves mlimited confused than usual. Does anyone have a proposed mechanism for why we observe three to five year surges in cases?

    That’s a good question that isn’t really understood. My guess would be that it has to do with the ebb and flow of susceptibles reaching a critical mass during peaks.

  12. #12 Heliantus
    September 5, 2012

    It was a typical Mercola bit of prestidigitation that, as so much antivaccine propaganda does, took a grain of truth […] and ran with it to construct a fantasy world

    That summarizes much of the usual modus operandi of alt-meds.
    Start from something real (vitamine C is good for you, cancer cells crave for glucose, vaccines have side-effects…) and just extrapolate an exponential curve from this single point.
    It makes rectifying their deluded theories all the more difficult.

  13. #13 dingo199
    September 5, 2012

    pD, the usual explanation for cyclic peaks of infectious disease is that there are regular epidemics which become established only when the herd immunity level has declined to a sufficiently low level to precipitate one, so it is a function primarily of the infectiousness of the agent (R0) and the duration of protective immunity following infection.

    This is rather simplistic, but in the prevaccine era we did see very regular cyclical patterns primarily for these reasons.

    However, things can get thrown off very easily. There is an underlying stochastic element to all these cycles, and population variables have an impact in a way they never did before. These include overall size of the population/communities, frequent movement in and out of populations, varying birth rates and therefore variable cohorts of infants, varying recognition and antibiotic treatment of cases affecting transmission dynamics etc, the picture can get muddled quickly.

    The clinical nature of pertussis cases is important too. We may always have seen largely asymptomatic or trivially symptomatic cases in adolescents/adults which were never diagnosed. These may have acted to help boost self and herd immunity. Today, because of greater awareness and better diagnostic techniques such as PCR there are more being diagnosed as clinical pertussis cases. However it is only those cases which have persistent cough/symptoms who may directly affect ongoing transmission, but even these cases are likely to be less infectious than a primary case of pertussis.

  14. #14 Todd W.
    http://harpocratesspeaks.com
    September 5, 2012

    @dingo199

    Pertussis could, theoretically, be eliminated, as there are no known non-human reservoirs. Granted, there are more strains than we currently immunize against, so completely wiping out pertussis is not something likely to happen in the near future. Then there are the related Bordetella species that produce illnesses similar to pertussis.

  15. #15 Heliantus
    September 5, 2012

    Finally, we should consider the potential contribution of genetic changes in circulating strains of B. pertussis

    Eh, if it’s true, it’s evolution in action: the strains which are able to bypass whatever we use to keep them at bay are being selected.
    We don’t exist in a vacuum, but as part of a big ecosystem, so that would not be a surprising discovery. Welcome to round 2 of the fight :-)
    It’s an issue, but one we can handle. To some extent, we are confronted with something similar with influenza – a pathogen whose dominant strains keep changing from year to year.

    I was reading somewhere how prevention measures for HIV are much better than post-infection treatment, from a natural selection prospective:
    – with prevention, you limit the number of people the pathogen have access to. Aggressive strains will be less likely to propagate, as they are more likely to kill their host before he/she meet someone they can infect. So we end up selecting strains which do less damage to the host.
    – if focusing on treatment only, we are more likely to select aggressive, fast-replicating strains, as their time is limited: the pathogen needs to jump to a different host before the current host receives medication.

    Conclusion: don’t bypass prevention. Even if it looks like it’s backfiring and the pathogens learn how to get around it. They will do it anyway with anything we do. And if we are lucky, we can force the pathogens to be more tame.
    Of course, allotting resources for both prevention and treatment is even better…

  16. #16 Heliantus
    September 5, 2012

    perspective, not prospective.
    Sorry, ESL. And me thinking I was bilingual. Still plenty of room for learning…

  17. #17 lkr
    September 5, 2012

    “Does anyone have a proposed mechanism for why we observe three to five year surges in cases?” — For juveline disease with initially high post-infection immunity, it takes a while to build up a supply of new customers. Think of [generally more regular] predator-prey cycles in the Arctic, or the re-release strategy of Disney cartoon features!

  18. #18 dingo199
    September 5, 2012

    pD, you might try and look at these articles, however I am struggling to even understand their titles, never mind the body of text!

    Opposite patterns of synchrony in sympatric disease metapopulations

    Persistence, chaos and synchrony in ecology and epidemiology

    ( I have stripped the links out as they seemed to get caught in the spam filter)

  19. #19 lilady
    September 5, 2012

    IMO, the implementation of the recommendations for a Tdap vaccine for children 11 years old and older and for any adult who expects to be caring for, or have close proximity to, an infant less than one year of age…is only a stopgap measure.
    In February, 2012 that Tdap boosting recommendation, in lieu of the 10 year Td booster, was extended to those age 65 and older.

    Presently, the Tdap booster is a “one time only” booster. The CDC, IMO, will have to recommend Tdap boosters every 10 years, in place of, the every-ten-year Td boosters.

    Here’s a CDC website showing States with enhanced surveillance activities:

    http://www.cdc.gov/pertussis/surv-reporting.html

    Enhanced Pertussis Surveillance (EPS)

    CDC has partnered with six states (CO, CT, MN, NM, NY, and OR) participating in the Emerging Infections Program (EIP) network to conduct enhanced surveillance of pertussis and other Bordetella species. EPS is characterized by enhanced case ascertainment and augmented data collection that goes beyond what is requested nationally through NNDSS. Participating sites collect isolates and specimens, when available, for further characterization at the CDC Pertussis and Diphtheria Laboratory. EPS sites also provide the infrastructure for conducting pertussis special studies including those aimed at evaluating pertussis prevention and control strategies.

  20. #20 Heliantus
    September 5, 2012

    @ Ikr

    the re-release strategy of Disney cartoon features

    I like the analogy. A good Disney movie sure can go viral :-)

  21. #21 lilady
    September 5, 2012

    The CDC has already provided some figures for uptake of Td 10-year boosters for individuals in various age groups, to evaluate the uptake of the newly recommended one-time dose of Tdap vaccine. The study was conducted to determine self-reported tetanus coverage by posing the question, “Have you received your tetanus shot within the last ten years?” We have a lot of work to do to encourage people to get their Tdap vaccine:

    http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5940a3.htm

  22. #22 Passionlessdrone
    The corner of dude and catastrophe
    September 5, 2012

    @science mom + dingo199 + lkr –

    Thanks and interesting thoughts. I guess (?) age adjusted rates over the surges might inform this question somewhat.

    I wonder, are there other childhood diseases that followed similar patterns? Maybe this is a function of my information filters that I don’t know the answer to this; are there (somewhat) predictable patterns to Hib, or diphtheria, or other diseases? Some patterns are pretty clear, flu in the winter, but other than that, I havent seen such temporal patterns mentioned for other

    If a waxing and waning susceptibe population is at the heart of this, shouldn’t a similar pattern be visible for lots of diseases? Does the fact that there are no known non human reservoirs inform this question in some way?

    @lkr – disney analogy very much appreciated.

  23. #23 Passionlessdrone
    September 5, 2012

    iPad / typos / trying to avoid the network overlords. Sorry.

  24. #24 Chris
    Neither here nor there...
    September 5, 2012

    pD:

    If a waxing and waning susceptibe population is at the heart of this, shouldn’t a similar pattern be visible for lots of diseases? Does the fact that there are no known non human reservoirs inform this question in some way?

    It is very common. If you look at the CDC Pink Book Appendix G you will see there are oscillations for measles and polio. In this old paper, Mass measles immunization in Los Angeles County, explains how they calculate susceptible numbers for an expected epidemic year.

  25. #25 Passionlessdrone
    September 5, 2012

    @chris –

    Very nice!

  26. #26 Science Mom
    http://justthevax.blogspot.com/
    September 5, 2012

    I wonder, are there other childhood diseases that followed similar patterns? Maybe this is a function of my information filters that I don’t know the answer to this; are there (somewhat) predictable patterns to Hib, or diphtheria, or other diseases? Some patterns are pretty clear, flu in the winter, but other than that, I havent seen such temporal patterns mentioned for other

    Measles had a cyclic ossilation but mass vaccination has interrupted that. Hepatitis A seems to have a ten year cycle. As far as I know, Hib and diphtheria do not have cycles but do have seasonal peaks. Meningococcal disease seems to have epidemic peaks in under-developed countries but not developed.

    If a waxing and waning susceptibe population is at the heart of this, shouldn’t a similar pattern be visible for lots of diseases? Does the fact that there are no known non human reservoirs inform this question in some way?

    A critical mass of susceptibles isn’t the only reason for some oscillations observed in infectious disease epidemiology. There are numerous other factors such as infectivity, host factors, immune duration and so on. For example, Hib disease is almost exclusively observed in children less than five years old. Children less than two years old do not adequately mount antibody responses to polysaccharide coats as what is on Hib and pneumococcal spp. This is a host factor. Hib is a transient commensal organism (not so much anymore but I’m thinking more pre-vaccine) which would periodically boost immune response as well as become an opportunistic pathogen. This is an ecological and infectivity factor. So you can see that it isn’t as straightforward as something like measles.

  27. #27 dingo199
    September 5, 2012

    More on measles epidemic cycles:
    http://asi23.ent.psu.edu/publ/bcf/bcf1.pdf
    http://asi23.ent.psu.edu/publ/bcf/bcf2.pdf

    Spoiled slightly by the authors’ inability to spell “Ipswich”

  28. #28 passionlessDrone
    September 5, 2012

    @Science Mom –

    http://i.imgur.com/3w1ej.gif

    – pD

  29. #29 dingo199
    September 5, 2012

    And another one, this time looking at how outbreaks will differ when they affect more highly vaccinated populations.
    http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.0020316

  30. #30 Science Mom
    http://justthevax.blogspot.com/
    September 5, 2012

    Very cute pD. :D

  31. #31 Hinterlander
    September 5, 2012

    Looking at these pertussis statistics, I wonder why boosters aren’t pushed more for adults – whether you have a baby in the family or not? This demographic must be quite a welcoming reservior for pertussis if boosters are neglected. Perhaps the health system is a bit more proactive beyond our shores, but here in NZ, boosters don’t seem to be pushed at all (correct me if I’m wrong Grant, Alison, et al.). I agree that the focus should be on the most vulnerable population, but what good is this if only a small portion of the herd are immune?

  32. #32 Todd W.
    http://harpocratesspeaks.com
    September 5, 2012

    @Hinterlander

    In the U.S., pertussis boosters for adults haven’t really been pushed until recently, when research started to discover that adults tended to be the ones passing pertussis along to kids, thanks to waning immunity (from either infection or vaccination) and the generally (though not always) milder manifestation in adults. For as long as I can recall, adults were only recommended to get Td boosters. A couple years ago, I had to ask my doctor for the Tdap instead (I decided to be proactive, considering the CA outbreak in 2010). Since then, when I’ve talked about pertussis or tetanus boosters with people, I always recommend that, if it’s been a few years, they ask their doctor for the Tdap, emphasizing that they should ask for a pertussis booster, so they get the right shot.

  33. #33 lilady
    September 5, 2012

    Yet another factor in measles outbreaks…with the history of the last major outbreaks late 1980s-early 1990s in the USA…which resulted in the decision to add a second dose of measles vaccine to the Recommended Childhood Vaccine Schedule:

    http://www.chop.edu/service/vaccine-education-center/a-look-at-each-vaccine/mmr-measles-mumps-and-rubella-vaccine.html

    “Why do children have to get two doses of MMR vaccine?

    In the early 1990s, a second dose of the MMR vaccine was recommended. This recommendation was made because outbreaks of measles swept across the United States in the late 1980s and early 1990s. Most of the people who were infected with measles during these epidemics were adolescents and young adults. An investigation of what went wrong found that many people who caught measles had never been immunized. So the primary reason for recommending a second dose of MMR was to give children two chances to get one vaccine.

    The other reason that a second dose of MMR vaccine was recommended was to allow for more children to develop a protective immune response. About 95 of every 100 children will develop immunity after one shot, but about 99 of 100 children will develop immunity to measles after two shots. Immunizing that additional 4 percent of children is important when trying to protect against a disease as highly contagious as measles.”

    The addition of mumps and rubella vaccines in this recommendation increases the percentage of children who develop immune responses to those viruses as well.

  34. #34 lilady
    September 5, 2012

    Misplaced quotation marks; need to close the quotation at the end of the last sentence of my post.

  35. #35 khan
    September 5, 2012

    I think I had whooping cough in mid 1990s; had vax in late 2010.

  36. #36 Hinterlander
    September 5, 2012

    @ Todd W.

    Hopefully NZ will follow suit soon. I’ve often thought that our Ministry of Health could use the annual flu vaccine media campaign to remind the public to check that their other vaccines/boosters are up to date. There are probably other confounding factors here such as funding, etc, that I’m overlooking.

    @ lilady – I never knew that about the MMR vaccine. That’s very interesting.

  37. #37 lilady
    September 5, 2012

    @ Hinterlander: IIRC, the second dose of mumps vaccine was recommended in the USA in 2006…because of large outbreaks in previous years and active surveillance of those outbreaks.

    Prior to that year, single antigen mumps, measles vaccines and rubella vaccines were still being manufactured and available in extremely limited number of doses.

    Imagine then, the parents who would search for and got single antigen vaccines for their children, because of their belief that triple antigen MMR shots could overload their children putting them at risk for autism. Most of the children (~ 95 %) were immune to measles with only 1-single antigen measles shot, verifiable by serum IGG levels indicating immunity, which was “proof” for school entry. In 2006 the second dose of mumps vaccine was recommended and there were no single antigen mumps vaccines available. So, they had to immunize with the combination MMR vaccine.

    You can easily look up all the Recommended Childhood Vaccines in the CDC Pink Book…an excellent reference for the histories of vaccines development.

    http://www.cdc.gov/vaccines/pubs/pinkbook/index.html

  38. #38 Daniel J. Andrews
    September 5, 2012

    “the only certainty in medicine (and life) is that all of us will one day die.”

    I’m hedging my bets on that one. So far so good.

  39. #39 alison
    September 6, 2012

    Hinterlander: here in NZ, boosters don’t seem to be pushed at all (correct me if I’m wrong Grant, Alison, et al.).

    I don’t think you’re wrong; when I’ve gone in for a tetanus booster (or had one perforce due to foolishness with sharp implements), I’ve never had even the breath of a suggestion that a pertussis booster would be in order. A combined vaccine is certainly available – http://www.immune.org.nz/vaccines/boostrix%C2%AE – so it’s odd that it’s never been offered to me (yes, yes, I know, anecdote!). Could be a cost issue, I suppose/

  40. #40 lilady
    September 6, 2012

    @ Alison: This is the 2012 CDC VFC (Vaccines For Children) Program price list. It lists costs per dose charged by vaccine manufacturers for Td, Tdap (and every other recommended childhood vaccine), for the VFC Program versus costs per dose for private providers.

    http://www.cdc.gov/vaccines/programs/vfc/awardees/vaccine-management/price-list/index.html

  41. #41 Grant
    September 6, 2012

    Regards the pertussis boosters and ‘cocooning’ in New Zealand, my impression was that there is no ‘mandatory’ boosters or cocooning, but it is encouraged, e.g. this from the IMAC pertussis page regards pregnant women and their families, at least for the Canterbury region:

    “All the young children in the household should be up to date with their childhood immunisations. Older children and adults in the household should have a tetanus, diphtheria, whooping cough vaccine too. However they have to buy their vaccine through their GP.”

    (I really must not self-promote… ah, stuff it: There was some discussion of this in media last year, which I wrote about. The journalist interviewed an anti-vaccine organisation spokesperson as ‘balance’; I choose to try position myself as someone without a strong science background [e.g. reporter/public] check out the spokesperson’s claims. Basically: “My exercise shows that readily-found sources, including one Rudgley recommends, contradict what she offered the journalist.”)

  42. #42 Chris
    Neither here nor there...
    September 6, 2012

    Grant, I was just looking at the NZ vaccine schedule, and it looks like they only give a Tdap at age eleven. While we in the USA are encouraged to get a tetanus booster every then years (which we pay for, unless we happened to have health insurance at the time), it seems your health service only provides it when you are 45 and 65 years old. And it is not the Tdap.

    Our system is often based on state policy. Last year I tried to get a Tdap from my family doctor, but he said it was too soon (my last Td was in 2005). So I got it at TAM9 in Las Vegas. Now there is a pertussis epidemic in my state and he wanted to give me a Tdap… it was interesting explaining that I got it a year before in Nevada!

    Well, I did try to get it before I went to “The Amazing Meeting”, where I met Orac and our Lord Draconis.

  43. #43 Hinterlander
    September 6, 2012

    @ Grant

    It would be good if this information was presented more at the coal face, so to speak. For example midwives or Plunket nurses could raise the subject of cocooning. The more the information is out there the more general consciousness is raised.

    @ Alison
    Well if we’re sharing anecdotes… :-) The nurse who administered vaccines at my old medical centre said that the varicella vaccine was really aimed at children who attend daycare, so that their parent’s wouldn’t have to take time off work if their child contracted the disease. Following that logic I shouldn’t have bothered having my daughter immunised for varicella as I’m working from home…

  44. #44 Colin Jenkins
    Wales, UK
    September 6, 2012

    I created a little ditty to model what @sciencemom explains above here – http://op12no2.me/toys/sir.php – the oscillations decrease in amplitude and frequency in the presence of vax with a side effect of the average age of infection going up – which is OK for pertussis but not CP. Recovery rate also increases freq which is probably why pertussis oscillations are generally > measles…?

  45. #45 Grant
    September 6, 2012

    Colin – nice work. Must have a peek at how you’re generating the graphs.

  46. #46 Nancy
    Boulder
    September 6, 2012

    My 11 year old recieved a pertussis booster 9 months ago. He has whooping cough and is very ill. Vaccines are not perfect. I think their effectiveness is diminished when a large percent of the population is not immunized.

  47. #47 Zach Miller
    September 6, 2012

    I actually just got my pertussis booster yesterday (I’m 29). Don’t know if I’ve ever had a booster, and the only ill effect I’ve felt so far is a little bit of soreness at the injection site.

    OH WAIT I also immediately developed autism, too. So there’s that. :-)

  48. #48 lilady
    September 6, 2012

    @ Nancy: I’m sorry that your son is ill. Was the diagnosis of pertussis confirmed by a laboratory test ordered by your doctor?

    Confirmatory laboratory tests are reported to local health departments and you will be hearing from a public health doctor or nurse. This person will be asking you about your son’s pertussis vaccines history.

  49. #49 Calli Arcale
    September 6, 2012

    Nancy — yes, if lots of people are unvaccinated, the vaccines are less effective. Well, the individual vaccines are just as effective either way, but the actual protection you get is definitely less if you’re the only one getting vaccinated than if everybody’s getting vaccinated.

    I hope your son gets better soon; pertussis *sucks*, plain an simple. I wish they could come up with a more effective vaccine; it’s a whole lot better than nothing; most people get immunity from it. But I wish the percentage was a lot higher.

  50. […] was reminded of the Nirvana Fallacy when it appeared in “Pertussis outbreaks and vaccine effectiveness”[1], posted in Respectful Insolence on September 5, 2102. The point of the article is that those […]

  51. #51 Lawrence
    September 7, 2012

    We may have a first developing over at the “Shot of Prevention” Blog. Our resident insane troll (Thingy) is getting into an argument with an ardent HIV & Germ Theory Denialist……this could be the first time I’ve ever seen that happen, could be very interesting to watch.

  52. #52 lilady
    September 7, 2012

    @ Lawrence: And how long did it take for the blog owner to send a tepid response. I’m half wanting to leave the sorry mess to the trolls.

  53. #53 dedicated lurker
    September 7, 2012

    Lawrence – linky please? This I must see.

  54. #54 Philip Rhodes
    September 8, 2012

    A study I was involved in (Bisgaard et al Pediatrics 2005) noted that one factor in the spread of pertussis was the presence of large households which were often the mixture of several (usually related) families.
    The financial and housing-mortgage meltdowns starting in 2007 resulted in many families moving from single-family residences to other situations such as multi-unit apartments or even multiple families in the same housing unit. This would have resulted in many older children/young adults being in closer contact with a wider range of individuals e.g. infants and adults whose immunity to pertussis would be low. Also, those older children/young adults with full histories of pertussis vaccination might also than have been in closer contact with older children/young adults who were under or even unvaccinated for pertussis.

  55. […] always reliable Orac demolishes more vaxxar […]

  56. #56 Tom Croll
    United Kingdom
    September 9, 2012

    It seems that the understanding of relative risk / benefit and efficacy are sadly becoming a rare competence among most of the population – and the situation is only going to get worse!

    The fact that the UK has just appointed a health minister who believes in homeopathy fills me with dread!

    http://londonskeptic.org.uk/uk-health-secretary-believes-in-magic-fairies

    If we can’t dissuade those elected to make informed decisions of blatantly ludicrous beliefs, what hope is there for more nuanced debate?

  57. #57 Calli Arcale
    September 10, 2012

    Tom — I do love, though, that he’s being described as the Minister of Magic. At least some of the general populace realizes how preposterous homeopathy is.

  58. #58 All Arms on Deck – Page 3.14
    September 13, 2012

    […] benefits, not an individual decision.”  Meanwhile, Orac deconstructs the fall and rise of pertussis infections in America. (0) More […]

  59. #59 pali
    November 28, 2012

    Would you say DR Maurice Hilleman of Merck was anti vaccine? After all he developed them then said the monkey component of the polio vaccine caused cancer through SV 40 virus exposure. I’m not sure where else I have had close contact with monkeys other than being vaccinated with their cells.

  60. #60 lilady
    November 28, 2012

    You got cancer from polio vaccine? Have you reported your cancer to the CDC?

  61. #61 Chris
    Neither here nor there...
    November 29, 2012

    Pali, Hilleman found SV40 in the vaccines, and then worked to make sure they were removed over fifty years ago! The “SV40″ bit is only outdates the thimerosal bit by forty years.

  62. #62 lilady
    November 29, 2012

    The “Danes” did it again. :-)

    http://jnci.oxfordjournals.org/content/95/7/532.abstract

    Cancer Incidence in Denmark Following Exposure to Poliovirus Vaccine Contaminated With Simian Virus 40

    Eric A. Engels,
    Hormuzd A. Katki,
    Nete M. Nielsen,
    Jeanette F. Winther,
    Henrik Hjalgrim,
    Flemming Gjerris,
    Philip S. Rosenberg and
    Morten Frisch

    “…..The relationship between exposure to SV40-contaminated vaccine and cancer incidence was evaluated by examining incidence in birth cohorts that differed in exposure to SV40-contaminated vaccine. In addition, cancer incidence was examined in children who were 0–4 years of age before, during, and after the period of vaccine contamination. Incidence was compared using Poisson regression, adjusting for age differences. All statistical tests were two-sided. Results: After 69.5 million person-years of follow-up, individuals exposed to SV40-contaminated poliovirus vaccine as infants (i.e., born 1955–1961) or children (i.e., born 1946–1952) had lower overall cancer risk (age-adjusted relative risk [RR] = 0.86, 95% confidence interval [CI] = 0.81 to 0.91 and RR = 0.79, 95% CI = 0.75 to 0.84, respectively; P<.001 for both) than unexposed individuals (i.e., born 1964–1970, after the vaccine was cleared of SV40 contamination). Specifically, SV40 exposure was not associated with increased incidence of mesothelioma, ependymoma, choroid plexus tumor, or non-Hodgkin’s lymphoma. After 19.5 million person-years of follow-up, incidence of all cancers combined, of intracranial tumors, and of leukemia among children aged 0–4 years was also not associated with SV40 exposure. Ependymoma incidence was higher during the exposed period than during the unexposed period (RR = 2.59, 95%CI = 1.36 to 4.92; P = .004 versus the period before contamination); however, incidence peaked in 1969, after the vaccine was cleared of SV40. Conclusion: Exposure to SV40-contaminated poliovirus vaccine in Denmark was not associated with increased cancer incidence….."

  63. #63 herr doktor bimler
    November 29, 2012

    Would you say DR Maurice Hilleman of Merck was anti vaccine? After all he developed them then said the monkey component of the polio vaccine caused cancer through SV 40 virus exposure.

    Perhaps you could link to the occasion on which Hilleman said polio vaccine causes cancer, so we will know that you’re not just another lying douchebag.

  64. #64 Krebiozen
    November 29, 2012

    There is an audio clip of an interview with Hilleman in which he makes some sarcastic comments about importing HIV and SV40 and about them causing cancer that are greeted with laughter by his audience. Hilleman had a very dry sense of humor which has been misinterpreted by idiots as Hillemman and his evil Big Pharma cronies cackling about the deaths he caused. Here’s deranged dentist Len Horowitz presenting the clip.

  65. #65 Chris
    Neither here nor there...
    November 29, 2012

    I would also remind Pali that this article is about pertussis. The only thing it has in common with polio (the vaccine that had SV40 in it until the early 1960s) is that the words both start with a “p.”

The site is currently under maintenance and will be back shortly. New comments have been disabled during this time, please check back soon.