Factors associated with maintenance of antibody responses to influenza vaccine in older, community-dwelling adults (BMC Infectious Diseases)

Background: Little is known about factors associated with maintenance of hemagglutinin inhibition (HAI) antibodies after influenza vaccination in older adults. Methods: Adults ≥50 years of age were vaccinated prior to the 2009–10 influenza season. Serum was drawn pre-vaccination (S1), 21–28 days post-vaccination (S2), and after the influenza season (S3) for HAI assays. Seroconversion was defined as ≥ 4-fold increase S1 to S2 or if S1