Comparative effectiveness and durability of COVID‐19 vaccination against death and severe disease in an ongoing nationwide mass vaccination campaign

As national coronavirus disease 2019 (COVID‐19) mass vaccination campaigns are rolled out, monitoring real‐world Vaccine Effectiveness (VE) and its durability is essential. We aimed to estimate COVID‐19 VE against severe disease and death in the Greek population, for all vaccines currently in use. Nationwide active surveillance and vaccination registry data during January–December 2021 were used to estimate VE via quasi‐Poisson regression, adjusted for age and calendar time. Interaction terms were included to assess VE by age group, against the “delta” severe acute respiratory syndrome coronavirus 2 variant and waning of VE over time. Two doses of BNT162b2, mRNA‐1273, or ChAdOx1 nCov‐19 vaccines offered very high (>90%) VE against both intubation and death across all age groups, similar against both “delta” and previous variants, with one‐dose Ad26.COV2.S slightly lower. VE waned over time but remained >80% at 6 months, and three doses increased VE again to near 100%. Vaccination prevented an estimated 19 691 COVID‐19 deaths (95% confidence interval: 18 890–20 788) over the study period. All approved vaccines offer strong and also durable protection against COVID‐19 severe disease and death. Every effort should be made to vaccinate the population with at least two doses, to reduce the mortality and morbidity impact of the pandemic.