Hard to say anything about the cause, but some will blame the vax, roids, whatever, but I don't think any one of us know for sure.
I think Brazilians are supposed to be extreme with the doses in a stupid and ignorant way (we feel), especially what some say about the fitness chicks stacks.
You see all those "Synthol" freaks in Brazil and the population seems pretty dumb to me. Not everyone lives in the favela like the Synthol boys, but maybe the genes overall aren't very stellar. Highly predjudiced of me I know. Maybe they don't consume much US media content wrt drug stacks so their approaches differ quite a bit from "us."