Effectiveness of COVID-19 vaccine mandates in raising vaccination rates among the elderly and general population in Europe: Controlled interrupted time series analysis

Abstract

Background: During the COVID-19 pandemic, three European countries (Austria, Greece, Italy) announced and/or implemented mandatory COVID-19 vaccination for high-risk groups in the general population. Besides the ethical justification for this policy, it is important to assess and quantify the effectiveness of the mandate in raising vaccination rates.

Methods: Controlled interrupted time series analysis of first-dose vaccination rates in the targeted age groups (Greece: ≥60 years; Italy: ≥50 years) relative to a control group (Greece: 50-59 years; Italy: 25-49 years) between week 35/2021 and week 50/2022. For Austria an uncontrolled analysis was performed, as the vaccine mandate targeted all adults ≥18 years.

Results: Announcement of mandatory vaccination substantially increased vaccination rates in the targeted age groups compared to control in both Greece (RR = 4.36, 95 % CI: 3.57-5.32) and Italy (RR = 2.90, 95 % CI: 2.37-3.56), an effect which persisted throughout the study period. There were 176,428 (95 % CI: 164,097-187,226) mandate-attributable first-dose vaccinations in Greece and 316,192 (95 % CI: 282,467-346,678) in Italy, most of which occurred before the mandate came into effect. In Austria no discernible increase in vaccination rates was observed after the announcement of mandatory vaccination. At the end of the study period, 9.5 % of ≥60 year-olds in Greece, 4.9 % of ≥50 year-olds in Italy and 13.8 % of ≥18 year-olds in Austria remained unvaccinated.

Conclusions: In Greece and Italy - though not in Austria - simple announcement of a vaccine mandate rapidly increased COVID-19 vaccination rates in the targeted age groups, without fully closing the vaccination gap. Mandatory vaccination appears to effectively target complacency but not vaccine hesitancy, and its public health benefits need to be weighted against possible detrimental effects on confidence and trust.

Keywords: COVID-19 vaccines; Ethics; Health impact assessment; Interrupted time series analysis; Mandatory programs; Primary prevention; Public health; Vaccination.