Brazil's death toll from Covid-19 passed 500,000 on Saturday and experts gave a warning that the world's second-deadliest outbreak may worsen owing to delayed vaccinations and the refusal by authorities to back social distancing measures.
Only 11 per cent of people in Brazil have been fully vaccinated and epidemiologists say the death toll will continue to rise even if the immunisation rate improves.
Brazil has registered 500,800 deaths from 17,883,750 confirmed Covid-19 cases, according to Health Ministry data on Saturday, the worst official death toll outside the US. Over the past week, Brazil averaged 2,000 deaths a day.
Covid-19 continues to devastate countries around the region, with the Pan American Health Organisation reporting 1.1 million new cases of Covid-19 and 31,000 deaths in the Americas last week.
Experts expect the number of fatalities in Brazil, already the highest in Latin America, to climb far higher.
"I think we are going to reach 700,000 or 800,000 deaths before we get to see the effects of vaccination," said Gonzalo Vecina, former head of Brazilian health regulator Anvisa.
"We are experiencing the arrival of these new variants and the Indian variant will send us for a loop."
Mr Vecina criticised far-right President Jair Bolsonaro's handling of the pandemic, including the lack of a co-ordinated national response and his scepticism towards vaccines, lockdowns and mask-wearing requirements, which he has sought to loosen.
Thousands of Brazilians across the country protested against Mr Bolsonaro's management of the outbreak on Saturday, blaming the government for the high death toll.
Raphael Guimaraes, a researcher at Brazilian biomedical centre Fiocruz, said delays in the vaccination programme in Latin America's most populous nation meant its full effects would not be felt until at least September.
He said Brazil could return to a situation similar to the worst of its March-April peak, when the country averaged 3,000 deaths a day.
"We are still in an extremely critical situation, with very high transmission rates and hospital bed occupancy that is still critical in many places," he said.
This week, new cases in Brazil increased to more than 70,000 a day on average, edging past India for the most in the world.
Vaccination will be crucial in beating the virus in Brazil, because the country has failed to reach a consensus on social distancing and masks, said Ester Sabino, an epidemiologist at the University of Sao Paulo.
"We really need to increase vaccination very quickly," she said.
But evidence from neighbouring Chile, which like Brazil has relied overwhelmingly on a vaccine developed by China's Sinovac Biotech, suggests it may be months before mass immunisation will effectively curb transmission.
Nearly half of the population of Chile has been vaccinated, but the capital Santiago has returned to lockdown after cases surged again to near peak levels.
Brazil will need to inoculate about 80 million people to reach Chile's current per capita vaccination levels.
That will require a more consistent supply of vaccines and ingredients in Brazil, which have been spotty in recent months, because imports from China were delayed after Mr Bolsonaro antagonised Beijing with comments perceived as anti-Chinese.