Vaccine

BackgroundThere have been inconsistent reports of decreased vaccine effectiveness (VE) against influenza viruses among older adults (aged 6565 years) compared with younger adults in the United States. A direct comparison of VE over multiple seasons is needed to assess the consistency of these observations.MethodsWe performed a pooled analysis of VE over 5 seasons among adults aged 6518 years who were systematically enrolled in the U.S. Flu VE Network. Outpatients with medically-attended acute respiratory illness (cough with illness onset 647 days prior to enrollment) were tested for influenza by reverse transcription polymerase chain reaction. We compared differences in VE and vaccine failures among older adult age group (65\u201374, 6575, and 6565 years) to adults aged 18\u201349 years by influenza type and subtype using interaction terms to test for statistical significance and stratified by prior season vaccination status.ResultsAnalysis included 20,022 adults aged 6518 years enrolled during the 2011\u201312 through 2015\u201316 influenza seasons; 4,785 (24%) tested positive for influenza. VE among patients aged 6565 years was not significantly lower than VE among patients aged 18\u201349 years against any subtype with no significant interaction of age and vaccination. VE against A(H3N2) viruses was 14% (95% confidence interval [CI] 1214% to 36%) for adults 6565 years and 21% (CI 9%-32%) for adults 18\u201349 years. VE against A(H1N1)pdm09 was 49% (95% CI 22%-66%) for adults 6565 years and 48% (95% CI 41%-54%) for adults 18\u201349 years and against B viruses was 62% (95% CI 44%\u201374%) for adults 6565 years and 55% (95% CI 45%-63%) for adults 18\u201349 years. There was no significant interaction of age and vaccination for separate strata of prior vaccination status.ConclusionsOver 5 seasons, influenza vaccination provided similar levels of protection among older and younger adults, with lower levels of protection against influenza A(H3N2) in all ages.U01 IP001034/IP/NCIRD CDC HHS/United StatesUL1 TR001857/TR/NCATS NIH HHS/United StatesU01 IP000473/IP/NCIRD CDC HHS/United StatesCC999999/Intramural CDC HHS/United StatesU01 IP000466/IP/NCIRD CDC HHS/United StatesU01 IP000471/IP/NCIRD CDC HHS/United StatesU01 IP000474/IP/NCIRD CDC HHS/United StatesU01 IP001035/IP/NCIRD CDC HHS/United StatesU01 IP001038/IP/NCIRD CDC HHS/United StatesU01 IP000467/IP/NCIRD CDC HHS/United States2019-02-28T00:00:00Z29402578PMC5812289vault:2623