RIO DE JANEIRO, BRAZIL – The coronavirus pandemic can be controlled if 75% of the population is vaccinated against Covid-19, according to a study carried out in a Brazilian city, where its inhabitants were massively immunized with the CoronaVac vaccine from the Chinese laboratory Sinovac, the Butantan Institute reported this Monday, May 31.
According to the study, the first of its kind to be carried out in the world, deaths fell by 95% after mass vaccination, hospitalizations dropped by 86%, and symptomatic cases were reduced by 80%.
The experiment also revealed that minors would not need to be immunized, because of the indirect effects of the vaccine.
The project took place in Serrana, a town located near Ribeirão Preto, some 200 km north of the state capital and home to 45,000 inhabitants, of whom about 30,000 over 18 years of age were immunized with the Chinese vaccine between February 17 and April 11.
Serrana was chosen for the study because it is a low-population city with high rates of Covid-19 infection.
One and a half months after the completion of the vaccination process in Serrana, the Butantan Institute, one of the most prestigious medical research centers in Brazil and Latin America, linked to the government of São Paulo and in charge of the manufacture of the Coronavac vaccine in Brazil, presented the conclusions on Monday at a press conference.
The so-called “Project S” (Serrana Project) vaccination process lasted four weeks, and in each of them, a group of adults was immunized. Control of the pandemic in the municipality was achieved when 75% of its population received the two doses of the Chinese immunizer, the study concluded.
Those responsible for the study compared the data from the beginning of the project – until the vaccination of all groups was completed – with the rest of the evaluated quarter (February, March, and April 2021).
The data show that on February 16, one day before the mass vaccination process, this municipality had 57 deaths and 2,499 confirmed cases of the virus.
After immunization, cases dropped to 699 in March and 251 in April. Deaths plummeted from 30 to 6 in the same period.
The results also showed that the vaccination protects both adults who received the two doses of the Chinese immunizer and children and adolescents under 18 years of age who were not vaccinated.
As explained by the director of clinical trials of the Butantan Institute, Ricardo Palacios, the immunization generated a sort of “immune belt” in Serrana, “drastically reducing” the transmission of the virus in the municipality.
“The most important result was to understand that we can control the pandemic even without vaccinating the entire population. When 70% to 75% coverage was reached, the drop in incidence was noticed even in the last group that had not yet completed the vaccination schedule,” he said. “It will not be necessary to vaccinate minors,” he specified.
For the general director of the Butantan Institute, Dimas Covas, this shows that the CoronaVac vaccine “is safe, effective and efficient” and contributes to preventing the development of the disease, complications, and deaths among those infected.
“We now also know that it has a beneficial effect on the entire population, protecting both vaccinated and unvaccinated people and significantly reducing viral circulation,” he added.