SAO PAULO • A study of the residents of a small Brazilian town who were vaccinated with the shot made by Sinovac Biotech showed that the jab can control Covid-19 outbreaks more effectively than expected from clinical testing, giving another boost to the Chinese-made vaccine that is relied on by dozens of developing countries.
While neighbouring cities were hit hard by the pandemic, Serrana - a town of 45,000 people where the study was carried out by the Sao Paulo state government - saw deaths fall by 95 per cent in the five weeks after the mass vaccination was completed. Symptomatic cases dropped by 80 per cent and hospitalisations fell by 86 per cent.
About 75 per cent of the town's residents were fully vaccinated; of the target adult population, 95 per cent came forward to receive both doses. No severe side effects from the vaccine were reported, and there were no Covid-19-related deaths among participants 14 days after the second dose was applied.
The area around Serrana, about 315km from Sao Paulo city, was overrun by the P1 variant of the coronavirus during the study, affirming the jab's effectiveness against the strain first found in Brazil, said Butantan Institute research director Ricardo Palacios.
"Now we can say that it's possible to control the pandemic with vaccines," Dr Palacios said, adding that Covid-19 numbers also fell for children. "This shows that it isn't necessary to vaccinate children to open schools."
The Serrana study may offer clues for other developing nations on how much of the public must be vaccinated to begin moving past the pandemic that continues to wreak havoc in Latin America and beyond.
It is also the latest in a string of real-world evidence validating the Sinovac shot, which only just cleared the minimum 50 per cent efficacy threshold in clinical trials, the lowest among first-generation Covid-19 vaccines.
In contrast, the efficacy rates for vaccines approved for emergency use by the World Health Organisation, such as Pfizer-BioNtech and Moderna, were more than 90 per cent, while the Oxford-AstraZeneca and Johnson & Johnson vaccines had efficacy rates of more than 60 per cent.
How well Sinovac's shot, known as CoronaVac, works is a high-stakes question for the developing world, which is largely reliant on it.
The Chinese vaccine, made using the traditional method of injecting an inactivated form of the virus to stimulate immune response, came under intense international scrutiny and criticism early this year after its clinical trials across Brazil, Turkey and Indonesia put its efficacy anywhere from 50 per cent to more than 90 per cent.
The company and its trial partners did not address the discrepancies, further fuelling doubt.