The Role of Social Contacts and Original Antigenic Sin in Shaping the Age Pattern of Immunity to Seasonal Influenza
Grey bars indicate observed seropositivity (proportion with HI titre >40) in each age cohort, with binomial confidence intervals given by black error bars. Blue lines show the age profile of immunity predicted by the best fitting model. The test year is 2005 for Finland and 2009 for Australia. A, proportion seropositive to H1N1/01 (New Cal./99-like strain) in Finland; B, H1N1/New Caledonia/99 in Australia; C, H1N1/Brisbane/07 in Australia; D, H3N2/00 (Panama/99-like) in Finland; E, H3N2/Wisconsin/05 in Australia; F, H3N2/Brisbane/07 in Australia.