Is Oxford-AstraZeneca Vaccine Effective in South American Countries?

Vaccine effectiveness was analyzed in the community of Complexo da Maré in Rio de Janeiro, at a time when the Delta and Gamma variants were predominant.

The COVID-19 pandemic has transformed our lives drastically. We have to improve and boost our immunity levels and vaccination against it is necessary and currently is an ongoing process for all countries.

Vaccinations were mandatory in some countries but in low- and middle-income South American countries including Brazil and Latin America, the cost and the availability of vaccines were high.

‘Large numbers of people in low- and middle-income countries live in densely populated favelas, often with limited resources to respond to the stress caused by COVID-19 pandemic.’

The Oxford-AstraZeneca Vaccine is also effective and shows promising results in reducing symptomatic COVID-19 in a socially vulnerable community where viral transmission is high and access to health and healthcare units might be low. This was found out by a study performed in a group of favelas (slums) in Brazil and co-led by ISGlobal, supported by the "la Caixa” Foundation, and the Oswaldo Cruz Foundation in Brazil (Fiocruz).

Large numbers of people in low- and middle-income countries live in densely populated favelas, often with limited resources to respond to the stress caused by COVID-19 pandemic. “We know that socially vulnerable populations have been disproportionately affected by the COVID-19 pandemic – they are more exposed to the virus and are more likely to die if they get sick,” says ISGlobal Researcher Otavio Ranzani, “but studies estimating vaccine effectiveness in these populations are lacking,” he said additionally. Furthermore, some studies have evaluated the vaccine efficacy against Gamma variant, which are mainly prevalent in Brazil and Latin America, and are somewhat able to escape recognition by vaccine-induced antibodies.

At the time of both Delta and Gamma were major variants in circulating the country, Ranzani and colleagues in Brazil aimed to test the effectiveness of the Oxford-Astrogeneca vaccine in socially vulnerable populations were studied. In order to do so, they focused on the Complexo da Maré Community, one of the largest group of slums in Rio de Janeiro and one of the areas with the highest number of COVID-19 cases and deaths. Thanks to the efforts of civil society, nongovernmental organizations, and the local community, a free trial strategy was implemented for 140,000 residents living in the area. In addition, a mass vaccination campaign between July and October 2021 was able to deliver two doses to 93.4% of adults, led by ongoing projects in Complexo da Maré and supported by the Secretary of Health of Rio de Janeiro.

The analysis of the research team included 10,077 PCR tests that are of 64% from symptomatic individuals and 36% from no-symptom individuals (average age of 40), which are linked to the community-program testing and the vaccination campaign databases. After correcting certain factors such as age, gender, and infection, they found that protection 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 confirm the need of administering the second dose,” as told by Fernando Bozza, senior author from the Oswaldo Cruz Foundation. However, the analysis does not allow to estimate vaccine protection against serious diseases. ISGlobal and the Oswaldo Cruz Foundation are both contributing and further studies are needed.

Source-Medindia