Vaccination Rate and Incidence of COVID-19 and Case Fatality Rate (CFR): A Correlational Study Using Data From 2019 to 2021

Introduction: COVID-19 has infected over 300 million people and killed almost five million people worldwide. The rapid development and deployment of vaccines almost a year after the initial outbreak was poised to contain the pandemic and enable the mobilization of the people and the economy. Vaccine deployment and containment of the pandemic have been far from uniform across the world. There is a lack of a clear understanding of the correlation between the COVID-19 vaccination rates and the incidence of the COVID-19 disease and COVID-19 mortality. Aim: The study aims to determine the correlation between the COVID-19 vaccination rate and the bi-weekly incidence rate of the COVID-19 disease to better understand the correlation between the vaccination rate and the COVID-19-related fatality in various countries. Materials and methods: Data from vaccination and the case fatality rate were abstracted until September 15, 2021, and from October 15 to October 31, respectively, for the various countries categorized based on their income levels. The bi-weekly COVID-19 incidence rate per million population and the case fatality rate was analyzed using SPSS version 27 (IBM Corp., Armonk, NY), followed by frequencies and percentages. Spearman rank correlation was used to determine the relationship between the variables. Results: A total of 191 countries were included in the study. The vaccination rate ranged from 0.03% to 82.1%, CFR from 0.14% to 32.1%, and the bi-weekly incidence rate ranged from zero to 1,283 per million population. A positive correlation was observed between vaccination rate and bi-weekly incidence rate (+0.57), whereas a negative correlation was observed between vaccination rate and CFR (-0.34). The results indicate a moderate positive correlation between vaccination rate and bi-weekly incidence rate and a weak negative correlation between vaccination rate and case fatality rate. Discussion and conclusion: Our study is interesting for the observation that the bi-weekly incidence rate of COVID-19 positively correlated with the rate of vaccination. In contrast, the vaccination rate correlated negatively with the case fatality rate. Although several factors may have contributed to the increased incidence rates for COVID-19, these observations refute the myth that COVID-19 vaccination offers complete protection from reinfection, especially in the backdrop of easing pandemic containment measures by some countries. An increase in the vaccination rate is certainly a positive contributor to the decreasing case fatality observed.