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…