Effectiveness of Cell-Based Quadrivalent Seasonal Influenza Vaccine: A Systematic Review and Meta-Analysis.

Cell-based seasonal influenza vaccine viruses may more closely match recommended vaccine strains than egg-based options. We sought to evaluate the effectiveness of seasonal cell-based quadrivalent influenza vaccine (QIVc), as reported in the published literature. A systematic literature review was conducted (PROSPERO CRD42020160851) to identify publications reporting on the effectiveness of QIVc in persons aged ≥6 months relative to no vaccination or to standard-dose, egg-based quadrivalent or trivalent influenza vaccines (QIVe/TIVe). Publications from between 1 January 2016 and 25 February 2022 were considered. The review identified 18 relevant publications spanning three influenza seasons from the 2017-2020 period, with an overall pooled relative vaccine effectiveness (rVE) of 8.4% (95% CI, 6.5-10.2%) for QIVc vs. QIVe/TIVe. Among persons aged 4-64 years, the pooled rVE was 16.2% (95% CI, 7.6-24.8%) for 2017-2018, 6.1% (4.9-7.3%) for 2018-2019, and 10.1% (6.3-14.0%) for 2019-2020. For adults aged ≥65 years, the pooled rVE was 9.9% (95% CI, 6.9-12.9%) in the egg-adapted 2017-2018 season, whereas there was no significant difference in 2018-2019. For persons aged 4-64 years, QIVc was consistently more effective than QIVe/TIVe over the three influenza seasons. For persons aged ≥65 years, protection with QIVc was greater than QIVe or TIVe during the 2017-2018 season and comparable in 2018-2019.