Health

São Paulo study: Mass vaccination slashed COVID-19 severity, deaths

Data on Serrana city show that 95% of cases were moderate

Agência Brasil

Published on 13/12/2022 - 13:10

- Updated on 13/12/2022 - 13:09

São Paulo

Funcionário de sáude aplica teste de Covid-19 durante bloqueio para impedir a difusão do coronavírus, em Auckland, Nova Zelândia — © Reuters/Fiona Goodall/ Direitos reservados

A study by Butantan Institute, recently published in the scientific journal Viruses, demonstrates that mass vaccination in the city of Serrana, São Paulo state, drastically reduced the number of severe cases and deaths caused by COVID-19.

The survey found that 95 percent of the cases identified in Serrana were mild—even when caused by the Omicron or Delta variants, which spread more rapidly.

For the study, scientists sequenced 4,375 samples from patients who tested positive for COVID-19 between June 2020 and April 2022. Of those, 1,653 cases showed the Delta variant, 1,053 Gamma, 1,513 Omicron, and 156 other strains.

Mass vaccination

The data also indicated that mass vaccination caused 88.9 percent of the cases linked the Gamma variant to be mild. Also mild were 98.1 percent of the occurrences related to the Delta variant, compared to 99.1 percent for Omicron.

The study, despite not being focused on vaccine effectiveness, but rather on a phylogenetic analysis—which examines the evolutionary development of the virus—demonstrated the positive impact of inoculation, the researchers said.

“Despite the epidemic waves in the time span surveyed, we observed that vaccination was instrumental in reducing morbidity, severe cases, and mortality,” they reported.

The results ratified a previous study, which found CoronaVac to be 80.5 percent effective against symptomatic cases of COVID-19, 95 percent effective against hospitalizations, and 94.9 percent effective against deaths caused by COVID-19.

Sublineages

The study also identified 52 Sars-CoV-2 sublineages circulating in the city of Serrana, including rare variants that had not been described elsewhere in the country.

“This casts light on the relevance of systemic monitoring of circulating strains, which provides key molecular and epidemiological information, helping us not only monitor rare strains, but also predict the introduction of variants of concern as well as future epidemic waves,” the article reads.

CoronaVac

Serrana was part of a clinical study that gauged the efficiency and effectiveness of CoronaVac, a vaccine produced by Butantan Institute and Chinese laboratory Sinovac. Dubbed Project S, the survey began in February last year, with the mass vaccination of the entire adult population of Serrana with CoronaVac.