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COVID-19 vaccine effectiveness against hospitalisation due to laboratory-confirmed SARS-CoV-2 infection in older adults: pooled results from eight European countries

Background : European vaccine effectiveness (VE) studies initiated and funded by the European Centre for Disease Prevention and Control (ECDC) and the European Commission (I-MOVE-COVID-19) include 38 hospitals across 13 European countries. Using a test-negative case–control design, we aimed to measure VE against hospitalisation due to COVID-19 in vaccination target group(s) overall and by vaccine product. Methods : Between 28 December 2020 and 06 June 2021, we recruited patients hospitalised with severe acute respiratory illness (SARI ; ECDC case definition). Cases were SARI patients, laboratory-confirmed SARS-CoV-2 positive by RT-PCR within 24 hrs of admission or within the previous 2 weeks. Controls were SARI patients who were RT-PCR negative for SARSCoV-2 at admission. We pooled available data received from 34 hospitals in eight countries, and estimated VE in those aged ≥65 years using logistic regression, adjusting for study site (as fixed effect), swab date, age and chronic condition. Results : We included 1, 670 SARI patients (1, 095 cases, 575 controls). Seventynine cases (7%) and 244 controls (42%) were vaccinated ; 73% (235/323) with Pfizer–BioNTech vaccine. Adjusted VE (aVE) for one and two doses of Pfizer–BioNTech was 69% (95%CI: 44–82) and 93% (95%CI: 85– 97), respectively (sample size was too small to estimate aVE by other vaccine products). For one dose of Pfizer–BioNTech, aVE was 73% (95%CI: 49– 86) in those aged 65–79 years and 64% (30–82) in those ≥80 years. For two doses in these age-groups, aVE was 97% (95%CI: 86–99) and 85% (95%CI: 66–94), respectively. Conclusions : Our results suggest good protection against severe COVID-19 conferred by one and two doses of Pfizer–BioNTech vaccine in adults ≥65 years.

SARS-CoV-2, COVID-19 vaccines, vaccine effectiveness, hospitalisation, multicentre study

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