Most cases of severe disease and mortality after infection with seasonal influenza A virus occur in the ≥65 years population. In contrast, 2009 H1N1 has not been associated with a large number of infections in this age group but has the highest attack and hospitalization rates in individuals between the ages of 0-40. The reduced number of cases in those aged ≥65 stems in part from the fact that antibodies generated to pre-1950 H1N1 viruses cross react with 2009 H1N1, resulting in limited protection from 2009 H1N1 infection [3] .