One way to prevent flu is to catch flu

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The way many of us are encouraged to get vaccinated against flu, we might imagine this practice is a failsafe way to avoid the condition. But we’d be wrong. As I wrote about recently here, flu vaccination is a lot less effective than we have generally been led to believe. Plus, it’s perhaps worth bearing in mind that many individuals need to be vaccinated for one person to benefit. In other words, the vast majority of people who are vaccinated against flu will not benefit.

More recently I wrote about an example of how flu vaccination can be reported in a way which puts it in a very positive light and perhaps fails to draw our attention to the fact that this practice is generally quite ineffective. This week I came across another article which has made me think again about the wisdom flu vaccination.

It concerned the supposed flu ‘pandemic’ of 2009. The virus responsible was of the HIN1 type, and was colloquially referred to a ‘swine flu’. Back in 1918, a similar flu strain caused an estimated 675,000 deaths in the US. Yet, in 2009, the ‘epidemic’ killed around 14,000 people – less than in some regular flu seasons. How come the 2009 virus had a much more benign effect than predicted?

There is evidence that catching a previous flu infection might have helped contain the HINI virus [1]. Researchers in America assessed 500-odd people during 2009 and 2010. The individuals were tested for the presence of antibodies in their blood to HINI viruses. These were individuals who had not been vaccinated, meaning the antibodies must have come from natural contact and infection with the flu virus.

In those without antibodies, 33 per cent of individuals succumbed to the HINI virus.

In those with antibodies, however, only 18 per cent succumbed to the HINI virus.

In other words, previous natural exposure to a HINI virus appeared to afford significant protection against infection with the particularly virulent H1N1 virus of 2009. And the authors of the study speculate that previous exposure may well have contributed to the relative mildness of that ‘pandemic’.

This of course raises the possibility that one way to protect ourselves from flu is to catch flu – which of course is part of the natural order of things.


1. Couch RB, et al. Prior infections with season influenza A/H1N1 virus reduced the illness severity and epidemic intensity of pandemic H1N1 influenza in healthy adults. Clinical Infectious Diseases 2011 epub 10th November 2011.

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