We observed decreased effectiveness of influenza vaccine with increasing time since vaccination for prevention of influenza A(H3N2), influenza A(H1N1)pdm09, and influenza B/Yamagata-associated hospitalizations among adults. Maximum vaccine effectiveness (VE) was observed shortly after vaccination, followed by an absolute decline in VE of about 8%-9% per month postvaccination.
Keywords: adults; hospitalization; influenza; vaccine effectiveness; waning.
Published by Oxford University Press for the Infectious Diseases Society of America 2021.