COVID-19 Vaccination and National-Level Long-Term Mortality

Background: Previous research has indicated that COVID-19 vaccination can reduce mortality, but diminishing protection and side effects have also been demonstrated. We can, therefore, not rule out that countries’ vaccination rates have affected mortality differently over time. That is, as vaccines may reduce national mortality temporarily, we know less about long-term effects. Methods: To study the research question, I used Our World in Data from 39 high-income countries and analysed them from early 2021 to the end of 2023. My motive for analysing those countries was relative homogeneity, presumably relatively high data quality, and, most importantly, they provided relatively consistent data during the study period. Analyses were weighted for population size. Results: From the last half of 2021 to February-March 2022, all-cause mortality was relatively low in countries with relatively high vaccination rates, which indicates temporal protection. However, a similar association concerning mortality excluding COVID-19 counters that explanation but not ruled out as it was less marked than between vaccination and all-cause excess mortality. From the beginning of March 2022, the vaccine rollout had stabilized, and since then, to the end of 2023, the mortality was consistently higher the higher the countries’ vaccination rate. The association was robust when controlling for alternative explanations. Conclusions: COVID-19 vaccination may induce limited short-term protection against mortality, but the long-term effect appears detrimental. As the analyses controlled for alternative explanations concerning the vaccine’s detrimental long-term mortality effect, ecological fallacy is not a major threat to the study’s internal validity.