Pooled vaccine effectiveness estimates against influenza A(H3N2) for people vaccinated in the current season only, and current and previous seasons, and the difference in these estimates
The reference group is people vaccinated in neither season. The previous season is defined as the influenza season immediately before the current season. The absolute difference in vaccine effectiveness (ΔVE) for people who were vaccinated in the current and previous (VECP) seasons and for those vaccinated in the current season only (VEC) was calculated as: ΔVE = VECP– VEC. Random-effect models for each vaccination group are presented pooled by current season and across all seasons. Fixed-effect models are only presented for pooled estimates across all seasons; for season-specific fixed-effect estimates see appendix (p 46). NR=not reported. RE model=random-effect model estimate. ΔVE=change in vaccine effectiveness. *Unadjusted vaccine effectiveness estimates are only presented in study.