AGÊNCIA FAPESP – Research carried out in Serrana (SP), a model city for immunization against Covid-19 in Brazil, proved that the mass vaccination it reduced death rates and severe cases of the disease even during the circulation of the gamma and delta variants, considered worrying due to their faster dissemination 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, in addition to monitoring the spread of the main variants of the virus in the city, it was possible 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 on the effectiveness of vaccination in Serrana carried out by Butantan Institute with the support of FAPESP