Department of Defense mid-season vaccine effectiveness estimates for the 2019-2020 influenza season.

This report provides mid-season vaccine effectiveness (VE) estimates from the Armed Forces Health Surveillance Division (AFHSD), the DoD Global Respiratory Pathogen Surveillance (DoDGRS) program, and the Naval Health Research Center (NHRC) for the 2019-2020 influenza season. Using a test negative case-control study design, the AFHSD performed a VE analysis for active component service members while the DoDGRS program and NHRC collaborated to perform a VE analysis for DoD beneficiaries and U.S.-Mexico border civilians. Among active component service members, there was low to moderate protection against influenza B, moderate protection against A(H3N2), and non-statistically significant low protection against influenza A overall and A(H1N1). Among DoD beneficiaries and U.S.-Mexico border civilians, there was statistically significant moderate protection against influenza B, influenza A overall, A(H1N1), and A(H3N2).