Analytical methods for pooled vaccine effectiveness stimates
We used a random-effects meta-analysis (Paule-Mandel method) to pool
site-specific aHRs, accounting from within and between sites variability
in the estimates. The number of sites contributing to the pooled
analysis for the different vaccination statuses at each follow-up period
varied due to differences in the national COVID-19 vaccination campaign
rollout (Supplementary material, Appendix 4). Only sites with general
recommendations of respective doses in 65–79-years and ≥80-year-old
were included in each eight-week observation period. Pooled VE estimates
obtained with fewer than 15 events were not reported.