A Brazilian town has seen a 95% drop in Covid-19 deaths after almost all adults were vaccinated as part of an experiment, researchers said.
Serrana, with 45,000 inhabitants, saw cases plunge after a mass vaccination with the Chinese-developed CoronaVac, reports the BBC.
The team said those who had not been vaccinated were also protected by the reduction in the virus's circulation.
The findings suggest the pandemic can be controlled after 75% of people are fully dosed.
Brazil has been hit hard by the pandemic, with nearly 463,000 deaths.
The country is struggling with a slow vaccination campaign due to insufficient jabs, while the average of daily deaths and cases remains high amid a lack of co-ordinated measures to curb infections.
The experiment in Serrana, in the south-eastern São Paulo state, was carried out between February and April by Instituto Butantan, which produces the CoronaVac vaccine developed by China's Sinovac Biotech.
The city was divided into four areas to help determine the threshold for containing the virus. The team said this was achieved after three areas, or about 75% of the population over the age of 18, had been given both doses.
When 95% of adults were fully vaccinated, they said the results showed that:Ricardo Palacios, research director at Butantan, said the key figure was the 75%.
"The most important result is that we can control the pandemic without having to vaccinate the whole population," he said.
Palacios also said there was a decline in the number of cases among children and teenagers, who had not been vaccinated. This could indicate that there was no need to vaccinate children for schools to reopen, he said.