Real-World Effectiveness of COVID-19 Vaccines: the Diverging Pattern of COVID-19 Cases and Deaths in Countries with High Vaccination Rates

Vaccines have played an important role in minimizing COVID-19 cases and deaths. Clinical trials of vaccines have suggested high efficacy against the SARS‑CoV‑2 virus. Here we evaluate the real-world efficacy of inactivated virus, viral vector, and mRNA COVID-19 vaccines. For our analysis, we chose 7 countries with a population > 1 million that have partially vaccinated ≥ 50% of their population by May 30, 2021. In some countries, the number of cases and deaths have declined significantly, whereas in others they have increased compared to the pre-vaccination levels. The data suggest that countries using mRNA-based vaccines have been the most effective in reducing the number of COVID-19 cases and deaths. The observed patterns could be due to the higher efficacy of mRNA-based vaccines. Additionally, the large difference in real-world and clinical trials for some of the vaccines can be attributed to the non-representative population sampling during clinical trials.