Effectiveness of ChAdOx1 vaccine in older adults during SARS-CoV-2 Gamma variant circulation in São Paulo

Matt D. T. Hitchings, Otavio T. Ranzani, Murilo Dorion, Tatiana Lang D’Agostini, Regiane Cardoso de Paula, Olivia Ferreira Pereira de Paula, Edlaine Faria de Moura Villela, Mario Sergio Scaramuzzini Torres, Silvano Barbosa de Oliveira, Wade Schulz, Maria Almiron, Rodrigo Said, Roberto Dias de Oliveira, Patricia Vieira Silva, Wildo Navegantes de Araújo, Jean Carlo Gorinchteyn, Jason R. Andrews, Derek A. T. Cummings, Albert I. Ko and Julio Croda ()
Additional contact information
Matt D. T. Hitchings: University of Florida
Otavio T. Ranzani: Barcelona Institute for Global Health, ISGlobal
Murilo Dorion: Yale School of Public Health
Tatiana Lang D’Agostini: Disease Control Coordination of the São Paulo State Department of Health
Regiane Cardoso de Paula: Disease Control Coordination of the São Paulo State Department of Health
Olivia Ferreira Pereira de Paula: Disease Control Coordination of the São Paulo State Department of Health
Edlaine Faria de Moura Villela: Disease Control Coordination of the São Paulo State Department of Health
Mario Sergio Scaramuzzini Torres: Municipal Health Secretary of Manaus
Silvano Barbosa de Oliveira: Pan American Health Organization
Wade Schulz: Yale University School of Medicine
Maria Almiron: Pan American Health Organization
Rodrigo Said: Pan American Health Organization
Roberto Dias de Oliveira: State University of Mato Grosso do Sul - UEMS
Patricia Vieira Silva: Universidade Federal de Mato Grosso do Sul - UFMS
Wildo Navegantes de Araújo: Pan American Health Organization
Jean Carlo Gorinchteyn: Health Secretariat of the State of São Paulo
Jason R. Andrews: Stanford University
Derek A. T. Cummings: University of Florida
Albert I. Ko: Yale School of Public Health
Julio Croda: Yale School of Public Health

Nature Communications, 2021, vol. 12, issue 1, 1-8

Abstract: Abstract A two-dose regimen of the Oxford-AstraZeneca (ChAdOx1) Covid-19 vaccine with an inter-dose interval of three months has been implemented in many countries with restricted vaccine supply. However, there is limited evidence for the effectiveness of ChAdOx1 by dose in elderly populations in countries with high prevalence of the Gamma variant of SARS-CoV-2. Here, we estimate ChAdOx1 effectiveness by dose against the primary endpoint of RT-PCR-confirmed Covid-19, and secondary endpoints of Covid-19 hospitalization and Covid-19-related death, in adults aged ≥60 years during an epidemic with high Gamma variant prevalence in São Paulo state, Brazil using a matched, test-negative case-control study. Starting 28 days after the first dose, effectiveness of a single dose of ChAdOx1 is 33.4% (95% CI, 26.4–39.7) against Covid-19, 55.1% (95% CI, 46.6–62.2) against hospitalization, and 61.8% (95% CI, 48.9–71.4) against death. Starting 14 days after the second dose, effectiveness of the two-dose schedule is 77.9% (95% CI, 69.2–84.2) against Covid-19, 87.6% (95% CI, 78.2–92.9) against hospitalization, and 93.6% (95% CI, 81.9–97.7) against death. Completion of the ChAdOx1 vaccine schedule affords significantly increased protection over a single dose against mild and severe Covid-19 outcomes in elderly individuals during widespread Gamma variant circulation.

Date: 2021
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DOI: 10.1038/s41467-021-26459-6

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