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Evaluation of a COVID-19 Vaccine Campaign and SARS-CoV-2 Infection and Mortality Among Adults Aged 60 Years And Older in a Middle-Income Country

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Key Points

Question  Is pragmatic, large-scale use of rAd26-rAd5, ChAdOx1, and BBIBP-CorV COVID-19 vaccines associated with reduction of morbidity, all-cause mortality, and COVID-19–related mortality in a population of individuals aged at least 60 years?

Findings  In this cohort study of 663 602 participants, the use of COVID-19 vaccines was associated with a significant reduction in all-cause death, COVID-related death, and documented infection with the use of 1 dose and even more with the use of 2 doses.

Meaning  These findings suggest that pragmatic use of available COVID-19 vaccines may significantly reduce morbidity and mortality.

Abstract

Importance  Although there are reports of COVID-19 vaccine implementation in real-world populations, these come from high-income countries or from experience with messenger RNA technology vaccines. Data on outcomes of vaccine deployment in low- or middle-income countries are lacking.

Objective  To assess whether the pragmatic application of the 3 COVID-19 vaccines available in Argentina, 2 of which have no reports of evaluation in real-world settings to date, were associated with a reduction in morbidity, all-cause mortality, and mortality due to COVID-19.

Design, Setting, and Participants  This cohort study used individual and ecological data to explore outcomes following vaccination with rAd26-rAd5, ChAdOx1, and BBIBP-CorV. To correct for differences in exposure times, results are shown using incidence density per 100 000 person-days from the start of the vaccination campaign (December 29, 2020) to the occurrence of an event or the end of follow-up (May 15, 2021). Participants included 663 602 people aged at least 60 years residing in the city of Buenos Aires, Argentina. Statistical analysis was performed from June 1 to June 15, 2021.

Main Outcomes and Measures  Diagnosis of COVID-19 confirmed by reverse transcription–polymerase chain reaction, death from all causes, and death within 30 days of a diagnosis of COVID-19. Poisson regression models were fitted to estimate associations with all 3 outcomes.

Results  Among 663 602 residents of the city of Buenos Aires included in the study, 540 792 (81.4%) were vaccinated with at least 1 dose, with 457 066 receiving 1 dose (mean [SD] age, 74.5 (8.9) years; 61.5% were female [n = 281 284]; 68.0% [n = 310 987] received the rAd26-rAd5 vaccine; 29.5% [n = 135 036] received ChAdOx1; 2.4% [n = 11 043] received BBIBP-CorV) and 83 726 receiving 2 doses (mean [SD] age, 73.4 [6.8] years; 63.5% were female [n = 53 204]). The incidence density of confirmed COVID-19 was 36.25 cases/100 000 person-days (95% CI, 35.80-36.70 cases/100 000 person-days) among those who did not receive a vaccine, 19.13 cases/100 000 person-days (95% CI, 18.63-19.62 cases/100 000 person-days) among those who received 1 dose, and 4.33 cases/100 000 person-days (95% CI, 3.85-4.81 cases/100 000 person-days) among those who received 2 doses. All-cause mortality was 11.74 cases/100 000 person-days (95% CI, 11.51-11.96 cases/100 000 person-days), 4.01 cases/100 000 person-days (95% CI, 3.78-4.24 cases/100 000 person-days) and 0.40 cases/100 000 person-days (95% CI, 0.26-0.55 cases/100 000 person-days). COVID-19–related-death rate was 2.31 cases/100 000 person-days (95% CI, 2.19-2.42 cases/100 000 person-days), 0.59 cases/100 000 person-days (95% CI, 0.50-0.67 cases/100 000 person-days), and 0.04 cases/100 000 person-days (95% CI, 0.0-0.09 cases/100 000 person-days) among the same groups. A 2-dose vaccination schedule was associated with an 88.1% (95% CI, 86.8%-89.2%) reduction in documented infection, 96.6% (95% CI, 95.3%-97.5%) reduction in all-cause death, and 98.3% (95% CI, 95.3%-99.4%) reduction in COVID-19–related death. A single dose was associated with a 47.2% (95% CI, 44.2%-50.1%) reduction in documented infection, 65.8% (95% CI, 61.7%-69.5%) reduction in all-cause death, and 74.5% (95% CI, 66%-80.8%) reduction in COVID-19–related death.

Conclusions and Relevance  This study found that within the first 5 months after the start of the vaccination campaign, vaccination was associated with a significant reduction in COVID-19 infection as well as a reduction in mortality.

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Article Information

Accepted for Publication: August 21, 2021.

Published: October 29, 2021. doi:10.1001/jamanetworkopen.2021.30800

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Macchia A et al. JAMA Network Open.

Corresponding Author: Alejandro Macchia, MD, Subsecretaría de Planificación Sanitaria y Gestión en Red – Ministerio de Salud de la Ciudad Autónoma de Buenos Aires, Ciudad Autónoma de Buenos Aires, Argentina (amacchia@buenosaires.gob.ar).

Author Contributions: Dr Macchia had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Macchia, Ferrante, Angeleri, Esteban, Rodríguez Tablado, González Bernaldo de Quirós.

Acquisition, analysis, or interpretation of data: Macchia, Angeleri, Biscayart, Mariani, Esteban, González Bernaldo de Quirós.

Drafting of the manuscript: Macchia, Biscayart.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Macchia, Ferrante, Mariani.

Administrative, technical, or material support: Angeleri, Biscayart.

Supervision: Ferrante, Rodríguez Tablado, González Bernaldo de Quirós.

Conflict of Interest Disclosures: None reported.

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