COVID-19 mRNA-vaccination and all-cause mortality in the adult population in Norway during 2021-2023: a population-based cohort study

IntroductionMost countries worldwide have experienced excess mortality that coincides temporally with the COVID-19 mass vaccination campaigns. This has led to speculation on the potential long-term effects of the vaccines on mortality risk. MethodsThe study was designed as a retrospective cohort study, and included all individuals aged [≥]18 years living in Norway during January 1, 2021, through December 31, 2023. Individuals were categorized as either unvaccinated (received no doses), partially vaccinated (received one or two doses) or fully vaccinated (received three or more doses) from the date of vaccination and onwards. Age-stratified Poisson models were used to estimate incidence rate ratios of death (all causes) between vaccination groups, adjusting for sex, calendar time, county of residence and risk group status (nursing home resident or preexisting condition with increased risk of severe COVID-19). ResultsThe study included 4 645 910 individuals (49.8% women) with 132 963 deaths during follow-up. There was a higher proportion of individuals that were part of a risk group among fully vaccinated individuals compared to unvaccinated individuals in all age groups, and a lower unadjusted rate of death: 51.5 vs 73.6 per 100 000 person years (py) among individuals aged 18-44 years, 295.1 vs 405.3 per 100 000 py among 45-64 years, and 3620.2 vs 4783.8 per 100 000 py among 65 years or older. The adjusted IRR of death for the same age groups were 0.42 (95% CI 0.38-0.47), 0.39 (95% CI 0.37-0.41) and 0.42 (95% CI 0.41-0.43), respectively. The differences in rate of death between vaccination groups were larger among men and peaked during 2022. ConclusionVaccinated individuals had a lower rate of all-cause death during 2021-2023 in Norway. Key messagesIn Norway, as in many Western countries, there has been an excess mortality during 2021-2023, surpassing the numerical count of COVID-19-associated deaths. The excess mortality coincides temporally with the COVID-19 mass vaccination campaigns, but longitudinal data regarding mortality post-vaccination remain sparse. Using real-time national health registry data, we estimate the risk of all-cause mortality by vaccination status in the total adult population in Norway during 2021-2023 and demonstrate a lower rate of all-cause death among vaccinated individuals.