Vaccination efforts in 17 countries saved up to 2.62 million lives, highlighting the critical role of vaccines in curbing the pandemic’s devastating toll.

Study: Estimated deaths averted in adults by COVID-19 vaccination in select Latin American and Caribbean Countries. Image Credit: Mongkolchon Akesin / Shutterstock

In a recent study published in the journal Open Forum Infectious Diseases, researchers used publicly available mortality and vaccination data from the coronavirus disease 2019 (COVID-19) pandemic to estimate the successful aversion of COVID-19-associated deaths in 17 select countries within the Latin American and Caribbean regions during the first year and a half after COVID-19 vaccines were made available in the region.

Background

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in early 2020 in China was declared a public health emergency by the World Health Organization (WHO). Subsequent transmission of the virus to other countries, the severity of the symptoms, and the high mortality rate resulted in the outbreak being declared a global pandemic.

Despite the rapid and concerted efforts to develop vaccines and therapies to combat COVID-19, the pandemic resulted in staggering mortality rates across the world and widespread socioeconomic losses. The estimated number of deaths due to COVID-19 is more than 7 million.

A significant portion of COVID-19-associated mortality occurred in the Americas, with the statistics from January 2023 indicating that close to 43%, or 2.8 million mortalities, were from the region. Of these, approximately 1.35 million deaths occurred in South America. The first COVID-19 vaccines became available in the Caribbean and Latin American regions in early 2021.

About the study

The present study aimed to estimate the number of COVID-19-associated deaths that were prevented by vaccination in 17 selected countries within Latin American and Caribbean regions, while addressing factors such as varied vaccination access and underreporting of deaths, as well as improvements in future vaccination campaigns and response assessments for COVID-19.

The researchers used a modeling approach to estimate the mortality averted due to COVID-19 vaccines between early 2021 and May 2022 in countries including Argentina, Brazil, Chile, and Uruguay, among others. The study focused on adults aged 18 and above. The data for the analysis were obtained from various sources, including the COVerAGE-DB global demographic database and the World Health Organization (WHO) Coronavirus Dashboard.

The data from COVerAGE-DB for countries such as Brazil, Argentina, and Chile were standardized by time periods and age. For countries such as Bolivia and Belize that lacked complete COVID-19-associated mortality data, non-age stratified estimates were used from the WHO dashboard, with age-stratified deaths imputed using a linear regression model.

The Pan-American Health Organization and Our World in Data were the two primary sources for the vaccination data in the region. PAHO provided age-stratified data starting from September 2021, while OWID provided more comprehensive but non-age-stratified data. The vaccine’s effectiveness in preventing death was categorized based on partial and full vaccinations and booster doses.

The models used in the study employed various equations to estimate the deaths prevented by COVID-19 vaccinations based on vaccination levels and effectiveness, as well as the number of reported deaths. One of the variables in the estimations was the proportion of vaccinated individuals in the population, which was further stratified based on partial or full vaccine coverage and booster doses. The study also accounted for the underreporting of COVID-19 deaths, using country-specific multipliers to adjust the reported figures.

Additionally, the varying effectiveness of different types of vaccines and the emergence of different SARS-CoV-2 variants of concern were also accounted for in the study through sensitivity analyses, which considered low, medium, and high vaccine effectiveness scenarios.

Results

The results indicated that the widespread administration of COVID-19 vaccines in the selected countries within the Caribbean and Latin American regions averted between 610,000 and 2.61 million deaths between early 2021 and May 2022. The models employed in the study predicted that without COVID-19 vaccinations, the COVID-19-related mortalities would have been around 2.67 million.

However, after the rollout of the COVID-19 vaccines in the region, only 1.05 million deaths had been reported, which, while being a substantial mortality rate in itself, was less than half of what the mortality rates could have been without the COVID-19 vaccines. After adjusting for underreporting, the actual number of COVID-19 deaths was estimated to be 1.49 million. Therefore, COVID-19 vaccines were estimated to have averted 273 deaths among every 100,000 individuals in the region.

The number of averted deaths also varied across the countries in the region. Countries such as Uruguay and Chile, where large percentages of the population had been vaccinated, experienced a higher number of averted deaths among those ages 60 years or older. For example, country-specific estimates reported that the vaccination campaign in Brazil resulted in over 70,000 averted deaths among individuals above the age of 60.

Despite the broad significance of these findings, the researchers believe that the study was limited in its ability to account for differing vaccine effectiveness based on different types of vaccines and the roles of natural immunity and vaccine waning in COVID-19-related deaths. The study also did not account for the role of factors such as herd immunity and COVID-19-associated lockdown measures in averting deaths during the COVID-19 pandemic.

Conclusions

To summarize, the study estimated that COVID-19 vaccines averted between 610,000 and 2.61 million deaths in the Caribbean and Latin American region between early 2021, when vaccines were made available in the region, and May 2022. These results corroborate the findings from other global and regional studies and reinforce the importance of COVID-19 vaccines in reducing the mortality associated with SARS-CoV-2 infections. The researchers highlight the need for continued evaluation of vaccination campaigns to better understand their effectiveness and inform future pandemic responses.