Scientific Publications by FDA Staff

J Infect Dis 2019 Sep 13;220(8):1255-64

Relative effectiveness of cell-cultured and egg-based influenza vaccines among the U.S. elderly, 2017-18.

Izurieta HS, Chillarige Y, Kelman J, Wei Y, Lu Y, Xu W, Lu M, Pratt D, Chu S, Wernecke M, MaCurdy T, Forshee R

BACKGROUND: The low influenza vaccine effectiveness (VE) observed during the A(H3N2)-dominated 2017-18 season may be due to vaccine virus adaptation to growth in eggs. We compared effectiveness of cell-cultured and egg-based vaccines among Medicare beneficiaries. METHODS: Retrospective cohort study on beneficiaries ages >/=65 years who received an influenza vaccine (cell-cultured, egg-based quadrivalent; egg-based high-dose, adjuvanted, or standard-dose trivalent) during the 2017-18 season. We used Poisson regression to evaluate relative VE (RVE) in preventing influenza hospital encounters. RESULTS: Of >13 million beneficiaries, RVE for cell-cultured vaccines relative to egg-based quadrivalent vaccines was 10% (95% CI: 7% to 13%). In a mid-season interim analysis, this estimate was 16.5% (95% CI: 10.3% to 22.2%). In a five-way comparison, cell-cultured (RVE 11%, 95% CI: 8% to 14%) and egg-based high-dose (RVE 8%, 95% CI: 7% to 10%) vaccines were more effective than egg-based quadrivalent vaccines. CONCLUSIONS : he modest VE difference between cell-cultured and egg-based vaccines only partially explains the low overall VE reported by CDC, suggesting egg adaptation was not the main contributor to the low VE found among individuals ages >/=65 years. The mid-season interim analysis we performed demonstrates that our methods can be used to evaluate VE actively during the flu season.