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.

Here, the authors investigate the effectiveness of the Oxford-AstraZeneca (ChAdOx1) vaccine during extensive Gamma variant SARS-CoV-2 circulation in São Paulo state, Brazil, and find that a two-dose regime is more effective than one dose against mild to severe Covid-19 outcomes in older adults.

Details

Title
Effectiveness of ChAdOx1 vaccine in older adults during SARS-CoV-2 Gamma variant circulation in São Paulo
Author
Hitchings Matt D T 1   VIAFID ORCID Logo  ; Ranzani, Otavio T 2   VIAFID ORCID Logo  ; Dorion Murilo 3 ; D’Agostini Tatiana Lang 4 ; de Paula Regiane Cardoso 4 ; de Paula Olivia Ferreira Pereira 4 ; de Moura Villela Edlaine Faria 4   VIAFID ORCID Logo  ; Torres Mario Sergio Scaramuzzini 5   VIAFID ORCID Logo  ; de Oliveira Silvano Barbosa 6 ; Schulz, Wade 7   VIAFID ORCID Logo  ; Almiron, Maria 8 ; Said, Rodrigo 8 ; de Oliveira Roberto Dias 9   VIAFID ORCID Logo  ; Silva, Patricia Vieira 10   VIAFID ORCID Logo  ; de Araújo Wildo Navegantes 11 ; Gorinchteyn, Jean Carlo 12 ; Andrews, Jason R 13   VIAFID ORCID Logo  ; Cummings Derek A T 14   VIAFID ORCID Logo  ; Ko, Albert I 15   VIAFID ORCID Logo  ; Croda Julio 16   VIAFID ORCID Logo 

1  University of Florida, Department of Biostatistics, College of Public Health & Health Professions, Gainesville, USA (GRID:grid.15276.37) (ISNI:0000 0004 1936 8091) 
2  Barcelona Institute for Global Health, ISGlobal, Barcelona, Spain (GRID:grid.434607.2) (ISNI:0000 0004 1763 3517); Universidade de São Paulo, Pulmonary Division, Heart Institute (InCor), Hospital das Clinicas HCFMUSP, Faculdade de Medicina, São Paulo, Brazil (GRID:grid.11899.38) (ISNI:0000 0004 1937 0722) 
3  Yale School of Public Health, Department of Epidemiology of Microbial Diseases, New Haven, USA (GRID:grid.47100.32) (ISNI:0000000419368710) 
4  Disease Control Coordination of the São Paulo State Department of Health, São Paulo, Brazil (GRID:grid.47100.32) 
5  Municipal Health Secretary of Manaus, Manaus, Brazil (GRID:grid.47100.32) 
6  Pan American Health Organization, Brasília, Brazil (GRID:grid.47100.32); Universidade de Brasília, Brasília, Brazil (GRID:grid.7632.0) (ISNI:0000 0001 2238 5157) 
7  Yale University School of Medicine, Department of Laboratory Medicine, New Haven, USA (GRID:grid.47100.32) (ISNI:0000000419368710) 
8  Pan American Health Organization, Brasília, Brazil (GRID:grid.47100.32) 
9  State University of Mato Grosso do Sul - UEMS, Dourados, Brazil (GRID:grid.473010.1) (ISNI:0000 0004 0615 3104) 
10  Universidade Federal de Mato Grosso do Sul - UFMS, Campo Grande, Brazil (GRID:grid.412352.3) (ISNI:0000 0001 2163 5978) 
11  Pan American Health Organization, Brasília, Brazil (GRID:grid.412352.3); Universidade de Brasília, Brasília, Brazil (GRID:grid.7632.0) (ISNI:0000 0001 2238 5157); National Institute for Science and Technology for Health Technology Assessment, Porto Alegre, Brazil (GRID:grid.7632.0) 
12  Health Secretariat of the State of São Paulo, São Paulo, Brazil (GRID:grid.7632.0) 
13  Stanford University, Division of Infectious Diseases and Geographic Medicine, Stanford, USA (GRID:grid.168010.e) (ISNI:0000000419368956) 
14  University of Florida, Department of Biology, Gainesville, USA (GRID:grid.15276.37) (ISNI:0000 0004 1936 8091); University of Florida, Emerging Pathogens Institute, Gainesville, USA (GRID:grid.15276.37) (ISNI:0000 0004 1936 8091) 
15  Yale School of Public Health, Department of Epidemiology of Microbial Diseases, New Haven, USA (GRID:grid.47100.32) (ISNI:0000000419368710); Instituto Gonçalo Moniz, Fundação Oswaldo Cruz, Salvador, Brazil (GRID:grid.418068.3) (ISNI:0000 0001 0723 0931) 
16  Yale School of Public Health, Department of Epidemiology of Microbial Diseases, New Haven, USA (GRID:grid.47100.32) (ISNI:0000000419368710); Universidade Federal de Mato Grosso do Sul - UFMS, Campo Grande, Brazil (GRID:grid.412352.3) (ISNI:0000 0001 2163 5978); Fiocruz Mato Grosso do Sul, Fundação Oswaldo Cruz, Campo Grande, Brazil (GRID:grid.418068.3) (ISNI:0000 0001 0723 0931) 
Publication year
2021
Publication date
2021
Publisher
Nature Publishing Group
e-ISSN
20411723
Source type
Scholarly Journal
Language of publication
English
DOI
https://doi.org/10.1038/s41467-021-26459-6
ProQuest document ID
2587482864
Copyright
© The Author(s) 2021. This work is published under http://creativecommons.org/licenses/by/4.0/ (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.