Posted by Any concerns about the current swine flu vaccine inevitably bring up the swine flu episode of 1976. This is not 1976. For starters, this year we have a bona fide pandemic and in 1976 the virus never got out of Fort Dix, NJ. That in itself is a game changer. If there are any risks from a vaccine (and there are usually some risks, even though they are much safer than most over the counter drugs) and they are for a disease no one is at risk for, the risk – benefit equation has nothing on one side and if there is anything, no matter how rare, on the other, it makes it unfavorable for the vaccine. But this year people are getting seriously ill by the tens of thousands and dying by the thousands from the virus and even if the vaccine were only 50% effective (and it is likely better than that), there is no contest. Vaccination wins.
Pandemic aside, 2009 does not seem to be like 1976 in the side effects area, either. The big issue in 1976 was the rare neurological problem, Guillain-Barré Syndrome (GBS):
Named after two French physicians who described it in 1916, Guillain-Barré syndrome causes weakness and tingling that starts in the legs, but over weeks can affect most of the body’s muscles. The symptoms occur because the insulation on the outside of nerve fibers breaks down, damaging the normal conduction of impulses.
In normal times, GBS occurs at a rate of roughly 2 cases per 100,000 people per year. Although only about 5 percent die, up to a third spend time in an intensive care unit on a ventilator before they get better. Nearly a third still have some weakness three years later.
After the 1976 vaccination campaign was halted on Dec. 16 of that year, much work went into figuring out whether the increase in GBS cases was real, or just a random upward blip.
Careful counting in defined populations — most important, the entire states of Minnesota and Michigan — proved beyond doubt that it was real: The risk of developing the condition rose four- to seven-fold in the six weeks after getting the swine flu shot. The number of cases attributable to the vaccine ranged from 5 to 12 per million people vaccinated. (David Brown, Blue Cross Blue Shield Newsletter)
Any disease that strikes on the order of 10 in a million is too rare for any pre-deployment testing (think about how big a clinical trial that would take). So the idea that the current vaccine is indeed safe is based on two main arguments. First, it is made by the same process and same manufacturers as the seasonal vaccine, which years of experience has shown to have an acceptable safety record. That process and the quality control for vaccines has changed since 1976. It’s better. And as for that routine seasonal vaccine, the swine flu version amounts to the kind of strain change we have seen many times as the seasonal vaccine is adjusted each year or two to account for the antigenic drift this virus undergoes routinely. There are no adjuvants or other changes that make this vaccine different.
The second argument is that current surveillance for adverse events suggests there is no unusual spike in serious adverse events in comparison to seasonal vaccines:
To assess the safety profile of H1N1 vaccines in the United States, CDC reviewed vaccine safety results for the H1N1 vaccines from 3,783 reports received through the U.S. Vaccine Adverse Event Reporting System (VAERS) and electronic data from 438,376 persons vaccinated in managed-care organizations in the Vaccine Safety Datalink (VSD), a large, population-based database with administrative and diagnostic data, in the first 2 months of reporting (as of November 24). VAERS data indicated 82 adverse event reports per 1 million H1N1 vaccine doses distributed, compared with 47 reports per 1 million seasonal influenza vaccine doses distributed. However, no substantial differences between H1N1 and seasonal influenza vaccines were noted in the proportion or types of serious adverse events reported. No increase in any adverse events under surveillance has been seen in VSD data. (CDC, Morbidity and Mortality Weekly Reports)
We are neither reassured or alarmed. There is insufficient data at the moment to make any judgement about rare events. If we saw something now it would have to be a very strong signal, the epidemiological equivalent to being whacked over the head with a two-by-four. The risks of the virus itself are two-by-four in size, so if you believe, as we do, that this vaccine works, even partially (and the evidence from trials is that the match is good and antibody response is robust), the risk – benefit equation is a no-brainer.
Having said that, we still don’t really know about adverse events. We have a pretty primitive reporting system that almost certainly under reports serious adverse events. It can take many weeks for GBS to show up post vaccination and we are just getting people vaccinated now, so it may be well after the campaign is over that we have a decent answer to this question — if then. We know so little about what causes GBS, which usually comes after some infection, that figuring out whether there still might be something different about a strain that comes from pigs that makes GBS more likely is a question that remains to be answered.
I do have another concern, which I voice with reluctance. I am looking very hard at whatever evidence and data are available, but it isn’t much. However the reassuring noises coming from CDC and WHO don’t make me feel any better. For too long there has been a cozy relationship between vaccine makers and both agencies and I sometimes worry that they are so deeply invested in the success of flu vaccines (not in the monetary sense but in the unshakeable belief sense) that it colors the way they report things.
I don’t automatically discount what they say because of this. Both CDC and WHO remain some of the best and most reliable sources of information on the vaccine program and the vaccines themselves. But I don’t automatically and uncritically accept everything they say about flu vaccines either. Right now we don’t know about the true rate of adverse events. I do feel confident — quite confident, in fact — that getting vaccinated for influenza makes rational sense for anyone. The imbalance of risks for the vaccine and the virus is so great — huge, in fact — that nothing else seems like rational behavior.
But I wish I had more confidence there’s no spinning going on. Given the facts, there’s no need to spin. Distancing themselves from the vaccine companies wouldn’t hurt. In fact it would help. A lot.
December 7, 2009
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