The effectiveness of COVID-19 vaccines in Latin America, 2021: a multicenter regional case-control study

Abstract

Background: As of September 2022, nearly 1.3 billion doses of COVID-19 vaccine products have been administered in Latin America and the Caribbean, where 27% of global COVID-19 deaths have occurred. This study aimed to estimate the effectiveness of COVID-19 vaccines against lab-confirmed COVID-19 related hospitalizations and deaths among adults in Argentina, Brazil, Chile, and Colombia.

Methods: Using a test-negative case control design, we evaluated the effectiveness of a primary vaccination series considering six COVID-19 vaccine products (Sputnik V, mRNA-1273, CoronaVac, ChAdOx1, BNT162b2, Ad26.COV2.S) against lab-confirmed COVID-19 hospitalizations and deaths among 83,708 hospitalized adults from February-December, 2021. Data from hospitalization records, COVID surveillance, and vaccination registries were used. Vaccine effectiveness was estimated using logistic regression ((1-OR) x 100).

Findings: The average age of participants was 56.7 (SD = 17.5), and 45,894 (54.8%) were male. Adjusted VE (aVE) estimates for full vaccination against hospitalization were 82% for mRNA-1273 (95% confidence interval (CI) = -30 to 98%), 76% (71%-81%) for BNT162b2, 65% (61-68%) for ChAdOx1, 57% (10-79%) for Sputnik V, 53% (50-56%) for CoronaVac, and 46% (23-62%) for Ad26.COV2.S. Estimates, particularly for CoronaVac, varied by variant. Decreasing aVE was estimated as age increased, particularly for CoronaVac and ChAdOx1. aVE estimates against death were generally higher, with 100% (CI not estimated) for mRNA-1273, 82% (69-90%) for BNT162b2, 73% (69-77%) for ChAdOx1, 65% (60-67%) for CoronaVac, 38% (-75 to 78%) for Sputnik V, 6% (-58 to 44%) for Ad26.COV2.S.

Interpretation: Primary series vaccination with available COVID-19 vaccine products was effective against COVID-19 hospitalization and mortality. Effectiveness varied by product and declined with increasing age.

Funding: This study was funded by the Pan-American Health Organization (PAHO, World Health Organization (WHO)). PAHO convened and led the study implementation.

Keywords: Argentina; Brazil; COVID-19 vaccination; Case–control; Chile; Colombia; Test-negative; Vaccine effectiveness.

Fig. 1

Pooled VE against lab-confirmed COVID-19 hospitalization, by vaccine product in use. Adjusted for continuous age, sex, secondary administrative unit location of residence, date of hospitalization grouped into categorical epiweeks, presence of 1 or more comorbidities, and study site country. Error bars show the 95% confidence intervals. Some estimates and/or 95% confidence intervals fall outside of the range 0–100% shown on the graph. These values can be found in Table 1. TND = test-negative design.

Fig. 2

COVID-19 vaccine effectiveness against lab-confirmed COVID-19 hospitalization, by vaccine product in use and by age group, Latin America, 2021. Adjusted for continuous age, sex, secondary administrative unit location of residence, date of hospitalization grouped into categorical epiweeks, presence of 1 or more comorbidities, and study site country. Error bars show the 95% confidence intervals. Some estimates and/or 95% confidence intervals fall outside of the range 0–100% shown on the graph. These values can be found in Table 2. TND = test-negative design.

Fig. 3

COVID-19 vaccine effectiveness against lab-confirmed COVID-19 death using all controls, by vaccine product in use. Latin America, 2021. Adjusted for continuous age, sex, secondary administrative unit location of residence, date of hospitalization grouped into categorical epiweeks, presence of 1 or more comorbidities, and study site country. Error bars show the 95% confidence intervals. Some estimates and/or 95% confidence intervals fall outside of the range 0-100% shown on the graph. These values can be found in Table 3. TND = test-negative design.

Fig. 4

COVID-19 vaccine effectiveness against lab-confirmed COVID-19 death, by vaccine product use, restricting to controls who died. Latin America, 2021. Adjusted for continuous age, sex, secondary administrative unit location of residence, date of hospitalization grouped into categorical epiweeks, presence of 1 or more comorbidities, and study site country. Error bars show the 95% confidence intervals. Some estimates and/or 95% confidence intervals fall outside of the range 0-100% shown on the graph. These values can be found in Table 4. TND = test-negative design.

Fig. 5

COVID-19 vaccine effectiveness against lab-confirmed COVID-19 hospitalization using syndrome negative (SN) controls, by vaccine product, in Chile and Brazil. Latin America, 2021. Adjusted for continuous age, sex, secondary administrative unit location of residence, date of hospitalization grouped into categorical epiweeks, presence of 1 or more comorbidities, and study site country. Error bars show the 95% confidence intervals. TND = test-negative design.