An average of 15% of Brazil’s 210 million people have COVID-19 antibodies, researchers announced on Wednesday.
The study, backed by the Sao Paulo state government’s research foundation (FAPESP) and Federal University of Sao Paulo (Unifesp), was conducted up to the end of April when contagion was on the rise.
Researchers found that the level of antibodies varied greatly across the country.
For example, in the northeastern state of Ceara, 9.89% of people had antibodies, compared with 31.4% in the northern state of Amazonas, which has been badly hit by the virus and even spawned a new homegrown variant known as the P1.
“These results show that there is a lot of spatial variation in the epidemic. We have several epidemics and not just one in Brazil,” said lead researcher Marcelo Burattini, a professor at Unifesp.
The presence of COVID-19 antibodies suggests that a person was likely infected with the virus at some point and may also mean the person has some immunity.
Brazil has been badly hit by the virus, with over 450 000 fatalities, the second-highest total in the world after the United States.
After months of denying the severity of the virus, President Jair Bolsonaro has been widely criticised for his handling of the pandemic, and for a slow and patchy vaccine rollout.
The study tested 120 000 people in 133 municipalities across the country between January 25 and April 24.
Burattini said the vast majority of people had not yet been vaccinated, since the tests were concentrated between January and mid-February, when the national vaccination program was just starting.
“Less than 1% of the people tested said they had received vaccines and virtually none of them had received both doses,” Burattini said.