Research carried out in Serrana (313 km from São Paulo), a model city for immunization against Covid-19 in Brazil, proved that mass vaccination reduced death rates and severe cases of the disease even during the circulation of the gamma and delta strains, considered to be of concern due to their faster spread than previous strains.
Based on the evolutionary analysis of Sars-CoV-2 (phylogenetics), the scientists showed that the virus replacement dynamics in the city was similar to the rest of the country.
It started with the ancestral lineages (B.1.1.28 and B.1.1.33) and then moved on to gamma, delta (detected in India in 2020 and originally named B.1.617.2) and, more recently, omicron.
However, in Serrana, the survey revealed that most cases for the three variants were mild —88.9%, 98.1%, 99.1%, respectively— thanks to immunization with Coronavac (Sinovac Biotech/Butantan Institute) which had reached 80% of the target population at the time.
The researchers performed analyzes on 4,375 complete genomes obtained between June 2020 and April 2022, a period that ranges from the initial introduction of Sars-CoV-2 to the vaccination process with at least two doses.
Through genomic surveillance, it was possible, in addition to monitoring the spread of the main variants of the virus in the city, to detect some rare ones, such as C.37, which circulated intensely in Andean countries, but without significant dissemination in Brazil. Or the alpha variant which, although detected locally, has not spread to other regions.
In all, 52 sublines of Sars-CoV-2 were identified in the city.
The research was published in the scientific journal Viruses and is part of Project S, an unprecedented clinical study of the effectiveness of vaccination in Serrana carried out by the Butantan Institute with the support of FAPESP. It had the participation of researchers from Butantan, the Blood Center of Ribeirão Preto (SP) and the Cell Therapy Center (CTC), a Research, Innovation and Dissemination Center (Cepid) of FAPESP linked to the Blood Center and the Hospital das Clínicas da Faculdade of Medicine of the University of Ribeirão Preto and São Paulo (FMRP-USP).
The city was used as a model for the studies, where, for the first time in Brazil, the Coronavac vaccine was applied en masse to adults over 18 years old, even before the start of the official vaccination program in the country.
A large-scale sequencing program was developed to investigate in real time all positive samples of Sars-CoV-2 obtained in the city.
“Next-generation sequencing, which allows genetic monitoring of many viral infections, is increasingly accessible and is widely used to detect viral genetic variations. Current technologies enable its wide use even in more remote territories and with few resources. Such a tool helps in the prevention and clarification of outbreaks, dissemination of new viral genotypes or in the identification of emerging viruses. Agência Fapesp Svetoslav Nanev Slavov, researcher at Butantan and first author of the article.
Results
Of the 4,375 genomes analyzed in the research, 1,653 cases were identified with the delta variant (37.8%), 1,053 of gamma (24.1%), 1,513 of omicron (34.6%), 75 of zeta (1.7% ) and 81 referring to other lineages (1.9%). Although there were participants of all ages, the majority were between 21 and 50 years old.
Based on the evaluation of the clinical score of the positive individuals, the researchers point out that the application of the vaccine was related to the reduction of morbidity and mortality, especially during the gamma and delta waves. Compare with the city of São José do Rio Preto (SP), about 200 kilometers from Serrana, where during the wave of the gamma variant there was a higher mortality rate, mainly among unvaccinated young people.
The beneficial effects of vaccination were observed in other studies, in which fully vaccinated individuals were less likely to acquire symptomatic or asymptomatic infections, showing effectiveness in reducing infection rates, severe cases and mortality related to Sars-CoV-2.
“In addition to carrying out genomic monitoring of positive cases of Sars-CoV-2 in the city of Serrana, the study showed the beneficial effects of vaccination which, when applied widely and early, can significantly reduce the mortality and morbidity rates of this agent. virus”, completes Simone Kashima, researcher at the Blood Center of Ribeirão Preto and corresponding author of the article.
For her, the work can serve as a basis for future studies aimed at genetic monitoring of viral infections and possible measures aimed at coping with them.
The article also had the support of FAPESP through seven projects (21/11944-6; 20/10127-1; 20/06441-2; 17/26950-6; 19/22155-2; 18/15826-5 and 14/50947-7).
12/10/2022 – Equilíbrio e Saúde