The Oxford-AstraZeneca COVID-19 Vaccine is effective in protecting socially vulnerable populations – EurekAlert

The Oxford-AstraZeneca vaccine is also effective in reducing symptomatic COVID-19 in a socially vulnerable community, where viral transmission is high and access to healthcare might be limited. This is the conclusion of astudyperformed in a group of favelas in Brazil, and co-led by ISGlobal, a centre supported by the la Caixa Foundation, and theOswaldo Cruz Foundation in Brazil(Fiocruz).

A large number of people in low- and middle-income countries live in densely populated slums or favelas, often withlimited resourcesto respond to the stress caused by a pandemic such as COVID-19. We know that socially vulnerable populations have been disproportionately affected by the COVID-19 pandemic they aremore exposed to the virus and are more likely to die if they get sick says ISGlobal researcherOtavio Ranzani, but studies estimating vaccine effectiveness in these populations are lacking, he adds. Moreover, few studies have assessed vaccine effectiveness against the Gamma variant, which circulated mainly in Brazil and Latin America, and is able to partially escape recognition by vaccine-induced antibodies.

In this study, Ranzani and colleagues in Brazil aimed to test the effectiveness of the Oxford-AstraZeneca vaccine in a socially vulnerable population, at a time when bothDeltaandGammawere the predominant variants circulating in the country. To do so, they focussed on the community ofComplexo da Mar, the largest group of slums inRio de Janeiroand one of the areas with the highest number of COVID-19 cases and deaths. Thanks to the efforts of civil society, NGOs and the local community, afree testing strategywas implemented for the 140,000 residents living in the area. In addition, amass vaccination campaignbetweenJuly and October 2021managed to cover 93.4% of adults with two doses, an action that was led by the projects ongoing in Complexo da Mar and supported by the Secretary of Health of Rio de Janeiro.

The research team linked the community-program testing database with the vaccination campaign database to perform their analysis, which included 10,077 PCR tests (64% from symptomatic individuals, and 36% from people who had no symptoms, with an average age of 40). After adjusting for certain factors such as age, sex and comorbidities, they found that theprotection against symptomatic COVID-19 was 31% after one dose and 65% after the second dose. Our estimates are in accordance with other studies of effectiveness of this vaccine with these variants of concern, and confirmthe need of administering the second dose, saysFernando Bozza, senior author from the Oswaldo Cruz Foundation. The analysis, however, did not allow to estimate vaccine protection against severe disease. ISGlobal and Oswaldo Cruz Foundation have an ongoing memorandum of agreement and further studies are expected.

Clinical Microbiology and Infection

Randomized controlled/clinical trial

People

Vaccine effectiveness of ChAdOx1 nCoV-19 against COVID-19 in a socially vulnerable community in Rio de Janeiro, Brazil: a test-negative design study

9-Feb-2022

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