Brazilian model vaccination program reduced s

Brazilian model vaccination program

image: The dynamics of SARS-CoV-2 variant substitution in the city where a vaccination effectiveness clinical trial was conducted matched the pattern seen in other parts of the country, but most cases were mild.
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Credit: Butantan Institute

A study conducted in Serrana, a small town in the state of São Paulo used as a model for vaccination against COVID-19 in Brazil, shows that mass vaccination reduced rates of severe cases and mortality even when gamma and delta variants were circulating . Gamma and delta were considered alarming because they spread much faster than previous variants.

Based on an analysis of the evolutionary history (phylogeny) of the virus, the researchers demonstrated that the substitution dynamics of SARS-CoV-2 in the city was similar to the pattern observed in the rest of Brazil. The ancestral strains (B.1.1.28 and B.1.1.33) were replaced by gamma, delta (first detected in India in 2020 and originally labeled B.1.617.2) and more recently omicron. In Serrana, however, the study showed that the majority of cases caused by the three variants (88.9%, 98.1% and 99.1% respectively) were mild, thanks to immunization with CoronaVac (Sinovac Biotech-Butantan Institute). Coverage had then reached 80% of the target population.

The phylogenetic analysis was applied to 4,375 genomes obtained between June 2020 and April 2022, the period between the introduction of SARS-CoV-2 and the completion of the double-dose vaccination process.

According to the authors, their genomic surveillance exercise not only monitored the spread of key variants in the city, but also helped identify some rare variants of interest, such as C.37, which circulated in the Andean countries but was underrepresented in Brazil. . , and alpha, which was detected in Serrana but did not spread to other places. In total, the scientists detected 52 SARS-CoV-2 sublineages in the city.

An article about the study is published In the diary virus. Codenamed Project S, the study was carried out by the Butantan Institute with support from FAPESP. The authors are researchers affiliated with the Butantan Institute, the Ribeirão Preto Blood Center and the Cell Therapy Center (CTC), Center for Research, Innovation and Diffusion (RIDC) funded by FAPESP and sponsored by the Ribeirão Preto Blood Center and Medical School of the University of São Paulo (FMRP-USP).

Serrana was a model for a clinical study of the first mass vaccination of the entire adult population of a town (over 18 years of age) using CoronaVac before the Ministry of Health began the official launch of the vaccine. A large-scale sequencing program was developed to analyze in real time all SARS-CoV-2 positive samples obtained locally (Read more at:

“Next-generation sequencing is becoming more affordable and widely used for genetic monitoring of infectious diseases and the viral variants involved. The technologies now available are applicable even in relatively remote areas with few resources. This type of surveillance helps us prevent outbreaks, understand how new viral genotypes spread, and identify emerging viruses. The detection of new viral agents and variants provides key information for public health decisions to avoid future pandemics or epidemics. Svetoslav Nanev Slavovfirst author of the article and a researcher at the Butantan Institute, said FAPESP Agency.


The 4,375 genomes analyzed in the study were broken down as follows by variant: 1,653 delta (37.8%), 1,053 gamma (24.1%), 1,513 omicron (34.6%), 75 zeta (1.7%) ) and 81 others (1.9%). Most of the subjects were in the 21-50 age group, although there were participants of all ages.

According to the authors, based on the clinical scores of the subjects who tested positive, vaccination reduced morbidity and mortality in Serrana, especially during gamma and delta waves. They compared the results with those of São José do Rio Preto, a medium-sized city about 200 km away, where mortality was higher during the gamma wave, especially among unvaccinated young people.

The beneficial effects of vaccination have been observed in other studies, demonstrating that fully vaccinated people are less likely to contract symptomatic or asymptomatic infections. The bottom line is that vaccination reduces infection rates, the number of severe cases, and death rates from SARS-CoV-2.

“In addition to the genomic follow-up of the patients who tested positive for SARS-CoV-2 in Serrana, the study demonstrated the benefits of early mass vaccination in the significant reduction of morbidity and mortality from this viral agent,” he said. simone kashimaLast author of the article and researcher at the Ribeirão Preto Blood Center.

The study serves as the basis for future research on the genetic monitoring of viral diseases and measures to combat them, he added.

The study also had the support of FAPESP through seven other projects (21/11944-6; 20/10127-1; 20/06441-2; 17/26950-6; 19/22155-2; 18/15826-5 Y 14/50947-7).

About the São Paulo Research Foundation (FAPESP)

The São Paulo Research Foundation (FAPESP) is a public institution whose mission is to support scientific research in all fields of knowledge by granting scholarships, grants and grants to researchers linked to State higher education and research institutions. from Sao Paulo, Brazil. FAPESP is aware that the best research can only be done by working with the best international researchers. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at and visit the FAPESP news agency at keep up to date with the latest scientific advances that FAPESP helps to achieve through its numerous programs, awards and research centers. You can also subscribe to the FAPESP news agency at

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