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
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 (hospitalisation and death), VE was estimated
monthly over eight-week follow-up periods, allowing one month-lag for
data consolidation. Cox proportional-hazards regression models were used
to estimate adjusted hazard ratios (aHR) and VE=(1 – aHR) x100.
Site-specific estimates were pooled using random-effects meta-analysis.
Results: For ≥80-years, 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. Multi-country data from EHR
facilitate robust near-real-time monitoring of VE in the EU/EEA and
supports public health decision-making.