Yesterday CDC had its last press conference of this calendar year on the flu pandemic (.mp3 here). CDC’s Anne Schuchat did her usual competent job and was generally upbeat while trying to maintain the need for urgency in the vaccination campaign. She cited numbers of over 100 million swine flu and 100 million seasonal flu doses having been produced for consumption in the US and this is a real accomplishment. She also noted that availability of swine flu vaccine was now much greater. Indeed my medical center notified us that it was generally available regardless of previous priorities. Hence I added swine flu vaccination to my previously obtained seasonal flu vaccination. I am now as immunologically defended by vaccines as I can be. With high flu activity still in about a fifth of the states but activity ebbing in many others, there is uncertainty about what will happen during the period that is normally the worst for seasonal influenza, January to March. Her answer when asked that is exactly right: no one knows.
Here are some possibilities. Swine flu comes roaring back in a third wave in January or February. This would be a repeat of the pattern of the 1957 pandemic where H2N2 appeared in the spring ebbed at mid summer, had a major recrudescence at the start of the school year and died down about the same time as this virus, and then had a big wave 3 during the “normal” flu season. Significantly the new pandemic virus replaced the H1N1 seasonal flu that had been circulating at least since 1918. Why should this year be different? It may not be. But in 1957 we weren’t able to produce a pandemic strain vaccine as we have this year. Getting a significant portion of the population vaccinated might, at the very least, flatten out and prolong the epidemic curve and lessen its impact. Moreover this year’s pandemic virus is an H1N1 subtype and another seasonal H1N1 subtype has been co-circulating in the population since 1977. We don’t know if either or both of these factors will alter the pattern we saw in 1957.
Another possibility, besides a repeat of 1957, would be a return of the two seasonal viruses, seasonal H1N1 and seasonal H3N2. Those viruses affect the entire population but unlike swine flu, hit the elderly portion much harder. So people my age (over 65) could suffer our usual toll of serious illness and death from the previously circulating seasonal viruses. So far those viruses are very little in evidence and we don’t know if they will come back. The reason I got the seasonal vaccine was to try to get some protection in case that happens. There is some evidence that any H3N2 seasonal virus is not an especially good match for the current seasonal vaccine, so protection there might be less than ideal, but the H1N1 and influenza B components appear to be good matches, although data are very sparse. Like everyone else, I don’t know, but my gut tells me there is a good chance this will happen. That would make for an unprecedented situation, the co-circulation of three influenza A viruses and influenza B.
A good portion of Schuchat’s message was that this period of somewhat decreased flu activity combined with increased vaccine availability is an excellent window of opportunity for anyone not vaccinated to get vaccinated. With the pandemic less in the news and the distractions of the holiday competing for our time, attention and storehouse of anxieties it is likely that vaccine “uptake” (the new jargon for actually getting vaccine into people) will slow and be yields to exhortation lessened. So if you are a parent who has yet to get your child or teen vaccinated (with two doses for the kids under 10 years old), we’ll leave you with a little added incentive:
Merry Christmas or whatever holiday you celebrate and may the New Year bring you and your family good health. Rather than leave it to chance or our good wishes, get vaccinated against influenza.