Seropositivity to influenza A(H1N1)pdm09 and influenza A (H3N2) and risk of infection in health care workers

BackgroundHealth care workers are at an increased risk of infection during influenza outbreaks. This study on seropositivity of influenza A viruses provided an opportunity to evaluate this risk.MethodsThis cross-sectional study was conducted during August–October 2013. Health care workers in a tertiary care center, Pondicherry completed a detailed questionnaire including sociodemographic and professional details, vaccination status, known history of swine or seasonal flu infection and contact with flu infected patients. Serum was collected and hemagglutination inhibition (HI) assaywas performed using reference antigens -influenza A (H1N1) A/California/07/2009, influenza A (H3N2) A/Victoria/361/2011 according to World Health Organization protocol. HI titres ≥40 were considered protective.ResultsSerum samples were received from 138 health care workers. Seropositivity to seasonal influenza A (H3N2) and pandemic influenza A(H1N1)pdm09 was 100% and 83% respectively. There was no association of any sociodemographic factor with seropositivity to influenza A viruses.ConclusionRegardless of sociodemographic, professional and vaccination status, most health care workers had seroprotective antibody titers against influenza A viruses, indicating that they are not at an increased risk of infection.