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

Abstract

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.

High vaccine effectiveness against severe COVID-19 in the elderly in Finland before and after the emergence of Omicron

“…Recent studies of adult populations have estimated the VE against severe COVID-19 caused by Omicron at 50-90% after the second dose [16,21,24,25,30] and at approximately 90% after the third dose [16,21,25,30]. Surprisingly, our results from the Omicron-dominated first quarter of 2022 match the upper limits of these estimates, although our study was restricted to elderly adults, in which VE is expected to be lower than that in younger adults [4,13,31]. High VE against severe COVID-19 caused by Omicron may partially explain the relatively low hospital burden during the Omicron wave in many European countries despite skyrocketing infection rates [32].…”

Healthcare system overstretch and in-hospital mortality of intubated COVID-19 patients in Greece: an updated analysis, September 2020 to April 2022

“…Our analysis reconfirms that being intubated outside an ICU is associated with twice higher mortality than patients inside an ICU, although again this must be interpreted with caution; patient selection (prioritizing for ICU admission those with a higher chance of survival) may account for a large part of this association. On the other hand, we found no statistically association between mortality and the number of COVID-19 vaccine doses received; this suggests that despite vaccination being enormously effective in preventing COVID-19 severe disease and death [7], if a patient has already been intubated as a result of COVID-19 severe disease, it is quality of care and not vaccination that can prevent further deterioration and death.…”

Understanding COVID-19 Vaccine Effectiveness against Death Using a Novel Measure: COVID Excess Mortality Percentage

“…Most studies on vaccine effectiveness against mortality (VE) have had limited controls for individual characteristics, often only age and gender [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ], or study short time periods [ 5 , 10 , 11 , 12 ]. U.S.-based studies typically lacked population-level data [ 7 , 13 , 14 , 15 ], and studies with population-level data often have had limited information about health status [ 3 , 4 , 8 , 9 , 16 ]. Some studies used a test-negative design [ 10 , 14 , 15 ], which is prone to selection bias [ 17 ].…”