Sep 09 2009
As the H1N1 flu pandemic of 2009 continues we are slowly learning more and more about it. The challenge is that health organizations and governments are trying to optimize their response to this flu strain in the midst of the pandemic unfolding. It’s like preparing for a hurricane as it’s happening, without knowing where it will make landfall, how strong it will be, how much water it will drop, and if the levies will hold. The best option is to prepare for the worst while hoping for the best.
There are two key features of flu strains that we track – infectiousness (how easily it spreads) and virulence (how severe an infection it causes, and specifically what is the percentage of hospitalizations and deaths). What we can say at this time about the current H1N1 strain is that it is about as infectious and virulent as the regular flu-season flu. This may make it seem like not such a big deal, but of course the regular flu season kills 36,000 people in the US alone, and about 400,000 world wide.
But as the pandemic unfolds we are learning some more details. Most flu deaths in regular flu seasons are among the elderly or in susceptible populations due to a chronic illness. The current H1N1 flu, however, disproportionately kills pregnant women and young children. Another pattern is also emerging – while in most people this strain causes a mild flu, in about 1% it results in a very severe flu with a 50% mortality rate. The severe cases develop a form of ARDS (acute respiratory distress syndrome) that destroys the alveoli (air sacs) in the lungs.
We cannot yet predict who will get the deadly form of the virus. It may be linked to genetic differences in the immune system, it may be anatomical, or it may just be bad luck – if the virus sets up an infection in the alveoli. If we could predict, that would enable us to give those who are susceptible and their families high priority in getting the vaccine.
The emergence of this severe response in 1% of the population is a cause for concern, not only because half of these people die, but because they are all severely sick and require hospitalization and even intensive care. If this pattern holds up, hospitals could be overwhelmed this flu season by young people needing ventilation.
All of this highlights the need for optimal use of the flu vaccine, and further highlights the danger of the absurd fearmongering that has been going on. The anti-vaccine and conspiracy crowds have been working overtime spreading misinformation about the H1N1 vaccine. Harriet Hall does an excellent job of taking down many of the false claims point by point. I have already written about the misinformation about GBS and the flu vaccine. And Joseph Albietz has written an excellent Influenza primer.
Unfortunately, it is easier to cause fear than to reassure with facts.
The bottom line is this: the H1N1 flu vaccine is likely to be reasonably safe and effective. While it is being fast tracked, it is using tried and true flu vaccine technology, and it is being actively studied in thousands of people. Further, the role out of the vaccine will be tracked to pick up any adverse effects as quickly as possible. Concerns about GBS are overblown, and we are likely to see the usual excess cases due to the vaccine of 1 in a million vaccinated.
The risks of the vaccine are small. Meanwhile the risks of the flu are significant – even if it remains just as virulent as it currently is. And, of course, the strain may become more virulent as it evolves throughout the flu season. The benefits of the vaccine outweigh the risks by orders of magnitude, but human psychology is not built to think rationally about such fears.
Anti-vaccine misinformation will have a real body count this flu season. That is a number we should track as well, so at least, maybe, we will learn something.
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