Study by Fiocruz at Maré attests to AstraZeneca's effectiveness

The first dose protects, but immunization requires a second dose and varies according to the age group and the time interval between doses. These are some conclusions of the pre-publication study that evaluated the effectiveness of the first dose of the AstraZeneca/Fiocruz vaccine against symptomatic cases of COVID-19 in the population of Complexo da Maré, in Rio de Janeiro (RJ). A 42.4% protection against symptomatic cases was estimated 21 days after the first dose of the vaccine. “It has a good result for containing symptomatic cases, but the second dose is essential to guarantee more complete immunity and broader protection for the community”, guarantees Fernando Bozza, coordinator of the study and researcher at Fiocruz.

The 42.4% effectiveness is in line with previous evaluations of the effectiveness of the first dose of AstraZeneca/Fiocruz in the context of the Gamma or Delta variant. It was also found that younger people had greater protection than older people. While in the population below 35 years the effectiveness was 57.5%, in the population above 35 years it was 34.8%. Another fact is that protection increases over time, from 40 days onwards. Effectiveness reaches 58.9%, considering all age groups above 18 years between days 42 and 55 after the first dose, and starts to drop after that.

Evaluating the impact of the pandemic specifically on vulnerable communities was also one of the objectives. More general data tend to neglect this particularity and homogenize contexts, which makes it difficult to adopt more effective policies for each reality. The study highlights that other analyzes have confirmed COVID-19 disproportionate impact on this type of community. “This is due to persistent social, economic and health inequalities”, highlights Fernando Bozza. “Although the effectiveness of vaccines has already been verified in high-income countries, there is a lack of papers estimating its effectiveness in contexts of greater vulnerability”, he explains.

The method employed by the study was the so-called negative test design (NTD), which compares patients who tested positive for COVID-19 with patients who did not test positive. The period covered, between January 17 and September 14, was characterized by a predominance of the Gamma and Delta variants.

Innovation in community involvement

The experience at Maré would be an exemplary case for the innovation in involving the community in the mobilization process for vaccination and for the study of its effectiveness. “This is the first study that estimates the vaccine's protection for the population of a neglected community that was heavily affected by the pandemic,” says Bozza. "When it comes to studies, there is a tendency to focus on numbers, results, but in this case, the entire process of working with primary care and mobilizing the population is very important.” For him, the involvement of the community in the research changed the perspective on the work and ensured more consistent results.

The study integrates a complex action by Fiocruz in the territory, with different dimensions of action and research. There are the vaccination campaigns themselves, as well as the engagement produced, and there are also studies, which occur together with vaccination, attesting to its effectiveness, through the monitoring of a group of families and the analysis of the virus circulation. Several ongoing studies make up the project, including one on the effectiveness of the second dose.

The study on the first dose began on January 17, 2021, with the general vaccination campaign in Rio de Janeiro, which, at Maré, until July, was reflected in the application of the first dose in 38% of the population and the second dose or single dose in 13%. With the Vacina Maré campaign, which mobilized the local community at the end of July through the action of the civil society organization Redes da Maré (Networks of Maré), Fiocruz and the Municipal Secretariats of Health and Education, around 37 thousand doses of the AstraZeneca vaccine were applied at more than 140 points, achieving 100% coverage of the adult population with at least one dose. In the period evaluated, which was until September 14, 2021, more than 136 thousand doses were administered, with more than 83 thousand from AstraZeneca, Fiocruz.

“The Maré project was very successful in the action process, of the vaccination of the first dose”, celebrates Bozza. “The goal was exceeded and 88% of people returned to the second dose. The work now is to individually search for people who missed the second dose, going to their homes or also through local influencers and communication strategies to ensure that we reach the entire population. The study, by measuring the protection of the first dose and showing the importance of completing the immunization process, reinforces the importance of these initiatives”, he concludes.