All vaccines against COVID-19 in Brazil require two doses to provide a sufficient level of antibodies. Whoever took the first dose of CoronaVac, the Sinovac vaccine produced locally by the Butantan Institute, must take the second dose of the same vaccine. The same goes for AZD1222, the immunizer from the University of Oxford and AstraZeneca produced in Brazil by FioCruz.

However, this guidance was not followed on at least 16,000 occasions. According to official data first gathered by Folha de S.Paulo and later confirmed by Brazil‘s Health Ministry, this is the number of Brazilians who had received switched doses of vaccines by the end of April, according to official data first gathered by Folha de S.Paulo and later confirmed by Brazil‘s Health Ministry.

According to experts, taking one dose of a vaccine and the second dose of another does not cause side effects or damage to health. The greatest risk would be collective, that is, the lack of complete protection to stop the pandemic in the country. So far, there is no official guidance on the matter.

To BBC Brazil, immunologist Cristina Bonorino said that this issue is being discussed among experts. “What we suggest to the ministry is that a technical note is issued in which the cases of people who received the switched doses are reported as a vaccine error and receive a third dose within the deadline set as ideal for each immunizer,” said the expert.