Seroprevalence of antibody to influenza A(H1N1) 2009 in Australian blood donors - before and after the 2009 influenza season, and prior to the 2010 Southern Hemisphere winter

摘要

Assessment of population exposure to the influenza A(H1N1) 2009 (pH1N1) outbreaks in Australia was made difficult by the generally mild nature of observed disease. We aimed to establish a representative collection of plasma samples from Australian Red Cross Blood Service donors within which to chart the proportion of the population with demonstrated immunity to the novel virus over a series of timepoints, from April 2009 to October 2010. We here present data up to the March/April 2010 timepoint. We compared reactivity to the novel virus strain using hae-magglutination inhibition (H1) assays performed on discarded plasma specimens left over from routine testing. Samples were taken from healthy adult blood donors (>16 years) before and after the pHlNl influenza epidemic that occurred during the Southern Hemisphere winter of 2009, and again prior to onset of the 2010 Southern Hemisphere influenza season. Reactivity to the novel H1N1 2009 strain of influenza was relatively uncommon among the healthy adult population during the first Australian winter wave, rising from a baseline of 12% to 22%. A further increase in the seropositive proportion from 22% to 43% was observed over the summer months, most likely attributable to immunisation. This level of immunity appears to have been sufficient to constrain the 2010 winter epidemic. Together with a final serum collection, planned for late 2010, these data will aid evaluation of the extent and severity of disease in this 'second wave' of pHlN1.