Background: Cell-derived influenza vaccines are not subject to egg-adaptive mutations that have potential to decrease vaccine effectiveness. This retrospective analysis estimated the relative vaccine effectiveness (rVE) of cell-derived quadrivalent influenza vaccine (IIV4c) compared to standard egg-derived quadrivalent influenza vaccines (IIV4e) among recipients aged 4-64 years in the United States during the 2019-2020 influenza season.
Methods: The IQVIA PharMetrics Plus administrative claims database was utilized. Study outcomes were assessed postvaccination through the end of the study period (7 March 2020). Inverse probability of treatment weighting (IPTW) was implemented to adjust for covariate imbalance. Adjusted rVE against influenza-related hospitalizations/emergency room (ER) visits and other clinical outcomes was estimated through IPTW-weighted Poisson regression models for the IIV4c and IIV4e cohorts and for the subgroup with ≥1 high-risk condition. Sensitivity analyses modifying the outcome assessment period as well as a doubly-robust analysis were also conducted. IPTW-weighted generalized linear models were used to estimate predicted annualized all-cause costs.
Results: The final sample comprised 1 150 134 IIV4c and 3 924 819 IIV4e recipients following IPTW adjustment. IIV4c was more effective in preventing influenza-related hospitalizations/ER visits as well as respiratory-related hospitalizations/ER visits compared to IIV4e. IIV4c was also more effective for the high-risk subgroup and across the sensitivity analyses. IIV4c was also associated with significantly lower annualized all-cause total costs compared to IIV4e (-$467), driven by lower costs for outpatient medical services and inpatient hospitalizations.
Conclusions: IIV4c was significantly more effective in preventing influenza-related hospitalizations/ER visits compared to IIV4e and was associated with significantly lower all-cause costs.
Keywords: cell-derived influenza vaccine; egg-derived influenza vaccine; healthcare costs; influenza; relative vaccine effectiveness.
© The Author(s) 2021. Published by Oxford University Press on behalf of Infectious Diseases Society of America.