Vaccine effectiveness of COVID-19 and rebound in the real world.

We intend to evaluate the relationship between the rates of global SARS-CoV-2 vaccination and the number of COVID-19 confirmed cases, as well as the mortality rate after the declaration of a pandemic. Of the data from 191 countries at the time of data retraction, we selected 111 countries that have SARS-CoV-2 vaccination reports. We stratified countries into high-income and non-high-income countries (HIC and non-HIC) based on World Bank income-group. We used a fixed-effects model (FEM) and performed a longitudinal analysis. The number of confirmed cases decreased as the vaccination rates increased in both non-HICs (B =  - 0.027, T =  - 2.0) and HICs (B =  - 0.207, T =  - 17.5). The number of deaths decreased as the vaccination rates increased in both non-HICs (B =  - 0.151, T =  - 2.3) and HICs (B =  - 0.230, T =  - 40.9). For full vaccination, this measure had a negative association with daily confirmed cases and daily deaths in both non-HICs and HICs. In non-HICs, daily cases and daily deaths decreased as the first vaccination and full vaccination coverages increased. However in HICs, daily cases and daily deaths decreased as the first vaccination and full vaccination coverages increased in the early phase, but after a certain period, they tended to increase again. We observed a significant association between the increase in vaccination coverage in the real world and reduced daily confirmed cases and deaths. However, as the confirmed cases and deaths have rebounded in HICs, our findings indicate that COVID-19 is not completely prevented through vaccine distribution.