Are You Older? So, Are You Immune to Swine Flu?

Those of us over 65 or 70 were happy to read that, perhaps, we might have a certain immunity to the H1N1 swine flu that’s “going around”. Of course, we’re really worrying about is the possible renaissance of the virus in a far more aggressive form in the fall. Usually influenza attacks the old and the young, with most of the deaths among the elderly. However, it looks as if the elderly have largely been spared by the new H1N1 swine virus; about 65% of cases are in people aged 5 to 24, and only 1% in those over 65.

In the Morbidity and Mortality Weekly Report the Centers for Disease Control (CDC) have reported the levels of antibody to the new virus in saved serum specimens from children and adults before and after they had been vaccinated with the 2005–06, 2006–07, 2007–08, or 2008–09 flu season vaccines. The results showed that before vaccination, no cross-reactive antibody to the new virus H1N1 existed among children. Among adults, before vaccination, cross-reactive antibody was detected in 6%–9% of those aged 18–64 years and in 33% of those older than 60.

This finding may explain the distribution of H1N1 swine flu in young vs. old persons. Maybe older individuals have some degree of immunity from years of vaccinations with seasonal flu vaccines, which contained a variety of H1N1 strains. Or perhaps a previous flu infection with an appropriate near-relative of the new virus confers some sort of immunity.

Cautiously, the deputy director for the relevant CDC department has stated: “The CDC does not believe that seasonal influenza vaccine would provide any meaningful protection against this novel H1N1 strain”. We’ll just have to wait and see – and get a shot against the new strain if one’s widely available in time.