Effectiveness of XBB.1.5 Monovalent COVID-19 Vaccines During a Period of XBB.1.5 Dominance in EU/EEA Countries, October to November 2023: A VEBIS-EHR Network Study

Using a common protocol across seven countries in the European Union/European Economic Area, we estimated XBB.1.5 monovalent vaccine effectiveness (VE) against COVID-19 hospitalisation and death in booster-eligible ≥ 65-year-olds, during October-November 2023. We linked electronic records to construct retrospective cohorts and used Cox models to estimate adjusted hazard ratios and derive VE. VE for COVID-19 hospitalisation and death was, respectively, 67% (95%CI: 58-74) and 67% (95%CI: 42-81) in 65- to 79-year-olds and 66% (95%CI: 57-73) and 72% (95%CI: 51-85) in ≥ 80-year-olds. Results indicate that periodic vaccination of individuals ≥ 65 years has an ongoing benefit and support current vaccination strategies in the EU/EEA.

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.