Efficacy of the CoronaVac® Vaccine in a Region of the Colombian Amazon, Was Herd Immunity Achieved?

Abstract Introduction. Currently, more than 1.8 billion doses of SARS-CoV-2 vaccines have been applied worldwide. However, some developing countries are still a long way from achieving herd immunity through vaccination. In some territories, such as the Colombian Amazon, mass immunization strategies have been implemented with the CoronaVac® vaccine. Due to its proximity to Brazil, where one of the variants of interest of SARS-CoV-2 circulates. Objective. To determine the efficacy of the CoronaVac® vaccine in a population of the Colombian Amazon. Methods. Between February 24, 2021, and May 19, 2021, a descriptive observational study was carried out in which a population of individuals over 18 years of age immunized with two doses of the CoronaVac® vaccine was evaluated. The study site was in the municipality of Mitú, Vaupés, in southeastern Colombia, a region located in the Amazon bordering Brazil. Results. 87% of the urban population of the Mitú municipality were vaccinated with CoronaVac®. To date, 2.1% of vaccinated individuals have become ill, and only 0.1% of these require hospitalization. No deaths attributable to COVID-19 have been reported among vaccinated individuals, and the vaccine has shown 97% efficacy against mild disease and 100% against severe infection. Conclusions. The herd immunity achieved through mass vaccination in this population has made it possible to reduce the rate of complicated cases and mortality from COVID-19 in this region of the Colombian Amazon.