The impact of the COVID-19 pandemic on influenza vaccination: A multi-year interrupted time series analysis

Abstract

Objective

To assess temporal changes in influenza vaccination coverage and evaluate differences by age and gender in the context of the COVID-19 pandemic.

Methods

We conducted a population-based interrupted time series analysis using data from Clalit Health Services in Israel. Adults aged ≥21 years were followed over 11 influenza seasons (2014-2015 to 2024-2025). Annual vaccination rates were stratified by age group (21-40, 41-64, ≥65) and gender. Segmented linear regression assessed changes before and after the pandemic onset. Counterfactual modeling estimated expected vaccination rates in the absence of the pandemic.

Results

Vaccination coverage declined from 26.2% (2014-2015) to 17.7% (2024-2025), despite a temporary rise to 28.7% in 2020-2021. Post-pandemic, rates decreased by 2.3 percentage points annually (p = 0.0013). The most pronounced drop was among adults aged ≥65, from 64.8% to 49.2%. Declines were observed across all age and gender groups. Interaction models showed no significant gender differences, but greater declines with increasing age. Counterfactual analysis estimated that 2024-2025 coverage was 5.7 percentage points lower than expected.

Conclusions

The COVID-19 pandemic was associated with a sustained decline in influenza vaccination uptake. Targeted strategies are needed to rebuild trust and restore routine immunization, especially among older adults.