Monitoring COVID‐19 vaccine effectiveness against COVID‐19 hospitalisation and death using electronic health registries in ≥65 years old population in six European countries, October 2021 to November 2022

BACKGROUND: Within the ECDC‐VEBIS project, we prospectively monitored vaccine effectiveness (VE) against COVID‐19 hospitalisation and COVID‐19‐related death using electronic health registries (EHR), between October 2021 and November 2022, in community‐dwelling residents aged 65–79 and ≥80 years in six European countries. METHODS: EHR linkage was used to construct population cohorts in Belgium, Denmark, Luxembourg, Navarre (Spain), Norway and Portugal. Using a common protocol, for each outcome, VE was estimated monthly over 8‐week follow‐up periods, allowing 1 month‐lag for data consolidation. Cox proportional‐hazards models were used to estimate adjusted hazard ratios (aHR) and VE = (1 − aHR) × 100%. Site‐specific estimates were pooled using random‐effects meta‐analysis. RESULTS: For ≥80 years, considering unvaccinated as the reference, VE against COVID‐19 hospitalisation decreased from 66.9% (95% CI: 60.1; 72.6) to 36.1% (95% CI: −27.3; 67.9) for the primary vaccination and from 95.6% (95% CI: 88.0; 98.4) to 67.7% (95% CI: 45.9; 80.8) for the first booster. Similar trends were observed for 65–79 years. The second booster VE against hospitalisation ranged between 82.0% (95% CI: 75.9; 87.0) and 83.9% (95% CI: 77.7; 88.4) for the ≥80 years and between 39.3% (95% CI: −3.9; 64.5) and 80.6% (95% CI: 67.2; 88.5) for 65–79 years. The first booster VE against COVID‐19‐related death declined over time for both age groups, while the second booster VE against death remained above 80% for the ≥80 years. CONCLUSIONS: Successive vaccine boosters played a relevant role in maintaining protection against COVID‐19 hospitalisation and death, in the context of decreasing VE over time. Multicountry data from EHR facilitate robust near‐real‐time VE monitoring in the EU/EEA and support public health decision‐making.