Wednesday, February 23, 2011

Fading Flu, and Hopes for a Vaccine

It is too early to sum up this year’s North American flu season, but so far, it is even more unremarkable than the previous one was. In 2009–2010, there was a lot of hype about H1N1 flu, but the peak of the infection had already passed in August, long before the beginning of the normal flu season. Then, the flu season itself was about one third lighter than an average flu season, based on both anecdotes and official statistics.

This season too has been unusually light, and some pathologists and epidemiologists believe this is not a coincidence. People who are known to have contracted the new H1N1 virus have had a much lower incidence of flu ever since. About one third of U.S. residents, and probably similar fractions in other North American countries, contracted H1N1 flu, even if they didn’t show symptoms. That’s an extraordinarily high infection rate for a virus that struck in the late spring and summer. The high infection rate of H1N1 led to thousands of deaths at the time, but now means there are a lot of people who have taken on some kind of new immunity to flu — so H1N1 has actually meant fewer flu deaths in the end.

Studying the virus itself, researchers say there appears to be something about it that lends immunity to a range of flu viruses, including many of the viruses in the record of the last century. If the researchers can pinpoint it, they may be able to use this particular feature of the virus to make a more broadly effective flu vaccine. It is important to note that the part of the virus surface that they are searching for is not something that is found in the existing H1N1 vaccine. People who received the vaccine, but who did not contract the flu, did not receive the additional immunity that H1N1 provides.

It can now be said that the tens of thousands of people who intentionally infected themselves with the H1N1 virus — a trend that was particularly strong in the United Kingdom — guessed right somehow. That’s a strategy I certainly would not want to encourage in the future, but it is curious that a crowdsourced answer to H1N1 turned out to be a more successful strategy than most of the measures public health experts were putting forward. I have to think there is a reason it worked out that way in this case, and surely someday scientists will have at least a guess of what that reason is.

There are other, completely unrelated efforts that also promise to produce a more effective flu vaccine, and there are several treatments being tested that may treat the virus after it has infected the body, when it is too late to use a traditional vaccine. One way or another, we may shortly have a partial answer for flu that is more effective than carefully washing hands and hand-contact surfaces all winter long. Even something that is only marginally effective can take the punch out of an epidemic by reducing the number of people available to transmit the virus to other people. So possibly, in a few years, flu may not be the fearsome force of nature that shadows most of us every winter season.