RIO DE JANEIRO, BRAZIL - A study by Chile's Catholic University has shown that the Chinese-developed Coronavac vaccine's effectiveness declines after six months, so patients may need a third dose of the immunizer.
Three out of four people who had received the vaccine still had neutralizing antibodies six months after the full treatment; however, after that point, the defenses against Covid-19 tend to disappear, particularly regarding new variants.
Coronavac protection is at its peak two weeks after the second dose and 42 days after the first one, but the levels of antibodies begin to fall from that . . .