Vaccination Impact on COVID-19 Mortality in Latin America and the Caribbean

The COVID-19 pandemic has affected global health, resulting in millions of deaths worldwide. This study estimates the number of lives saved through vaccination in the Latin America and Caribbean (LAC) region during the first 18 months of the vaccine rollout (January 2021 through May 2022). By providing a comprehensive assessment of the vaccine's impact on COVID-19 mortality in LAC, the results highlight the importance of timely and widespread vaccination in lowering fatalities. These findings are crucial for supporting vaccination initiatives against infectious diseases and preparing for future pandemics.¹

After adjusting for underreporting, the analysis revealed that over 1.49 million COVID-19 deaths occurred in the selected countries during the study period. The model estimated that without vaccination, deaths would have ranged from 2.10 to 4.11 million. Consequently, vaccination efforts are believed to have averted approximately 610,000 to 2.61 million deaths.¹

To estimate the total deaths averted by vaccination in LAC, publicly available data on COVID-19 fatalities and vaccination rates were analyzed. Using figures for total deaths, the number of vaccinated individuals, and vaccine effectiveness, a counterfactual estimate of deaths that would have occurred without vaccination was generated. Vaccine effectiveness estimates were obtained from published studies, focusing on 17 LAC countries and including adults aged 18 and older.¹

In an exclusive email interview with Contagion, Alexandra Savinkina, MSPH, PhD student specializing in the epidemiology of microbial diseases at the Yale School of Public Health, discusses this research further.

Could you specify the sources of data on COVID-19 deaths and vaccination rates used in your study, and how data accuracy was ensured across the 17 countries?

“COVID-19 data came from the COVerAGE-DB global database whenever possible. This data was reported directly by national governing agencies. This data was reported over time and by age group. For countries that did not have complete data in COVerAGE-DB, we used data as reported by the WHO. We were not able to directly check data for each country, and we do know that underreporting was a signficiant concern with reported COVID-19 deaths. We therefore additionally incorporated country-specific underreporting multipliers from Msemburi et al, and report results both with and without consideration of underreporting.”²

Can you elaborate on the methodology employed to estimate the counterfactual number of deaths that would have occurred without vaccination, including key assumptions and potential limitations?

“In order to estimate the counterfactual number of deaths that would have occurred without vaccination, we first calculated a proportion of the population that was protected from death via COVID-19 by taking the proportion of people vaccinated and the effectiveness of the vaccine. For instance, if 50% of people are vaccinated and the vaccine is 50% effective against death, then we assume 25% of the total population is protected against death from COVID-19. Then, we look at the observed number of deaths that occurred during this time period, with the assumption that only 75% of the population was able to die of COVID-19. We then take the assumption of the protected population away- this is the “no vaccine” scenario- and inflate the number of observed deaths to account for the proportion of people now vulnerable (for instance- 9 deaths at 75% vulnerable pop would become 12 deaths in the 100% vulnerable population- and this would mean that vaccination averted 3 deaths).”

How were vaccine effectiveness estimates obtained and applied in your analysis, and did these estimates vary by country or population?

“Vaccine effectiveness estimates came from the literature. We did not vary these estimates by country as there is limited data to allow for this. Instead, we included a wide range of effectiveness estimates to allow for the wide range of vaccines used.”

What methods were used to account for underreporting of deaths, and how did these adjustments affect your overall estimates?

“We used a multiplied to account for underreporting of deaths, with this data coming from Msemburi et al. When accounting for underreporting, our analysis showed a greater reduction in the magnitude of deaths.”

Did the impact of vaccination on mortality rates differ significantly among the 17 countries, and what factors might explain these variations?

“The impact of vaccination on mortality rates did differ among the 17 countries. The biggest factor appeared to be timing of vaccination: countries that were able to obtain the vaccine and vaccinate people earlier had a higher reduction in deaths, especially within the older population. In addition, countries that were able to vaccinate prior to a major COVID-19 outbreak were able to prevent more deaths- for instance, Chile had a high proportion of the population vaccinated prior to a spike in deaths, and our model shows this was able to prevent greater mortality.”

These findings support the need for ongoing vaccination initiatives and effective public health strategies to address current and future infectious diseases, offering insights for strengthening health systems in response to emerging challenges.

References

1. Alexandra Savinkina, Daniel M Weinberger, Cristiana M Toscano, Lucia H De Oliveira, Estimated deaths averted in adults by COVID-19 vaccination in select Latin American and Caribbean Countries, Open Forum Infectious Diseases, 2024;, ofae528, https://doi.org/10.1093/ofid/ofae528 

2. Msemburi W, Karlinsky A, Knutson V, Aleshin-Guendel S, Chatterji S, Wakefield J. The WHO estimates of excess mortality associated with the COVID-19 pandemic. Nature 2023; 613(7942): 130-7