Residual Immunity to H1N1 Swine Flu

An apparent residual immunity to H1N1 virus (swine flu) among the elderly has been reported. It's theorized that people born before the mid-1950s have at one time been exposed to H1N1 viruses which circulated from 1918 to 1957 and they consequently acquired an immune response which makes them less susceptible to the 2009 H1N1.

Anecdotally, almost the entire staff at a long-term care home in Ontario are believed to be infected and showing symptoms of H1N1 while all elderly residents are unaffected.

Therefore, the demographic group usually most at risk of flu (the elderly) are seemingly given a break with 2009 H1N1.

Heh.