After having Covid, know how long to wait to take a booster dose

Brazil faces an explosion of Covid cases driven by the omicron variant. In the midst of this scenario, vaccination against the virus continues.

With more than 67% of the Brazilian population vaccinated with the primary scheme —two doses or a single dose—, most people are preparing to receive the booster of the immunizer, which must be applied four months after the second dose.

However, according to a technical note from the Ministry of Health, those who have been infected by Covid-19 must postpone vaccination for at least four weeks after the onset of symptoms – asymptomatic people must wait four weeks from the first positive PCR test.

The note also highlights the need to wait for full clinical recovery to then take the additional dose if the illness lasts longer.

The guidance regarding the four-week interval in the case of those infected with Covid-19, in fact, does not depend on whether the patient is looking for the first, second or third dose.

Doctor Renato Kfouri, director of SBIm (Brazilian Society of Immunizations), explains that, if a person has symptoms of a cold and Covid-19 is ruled out, there is no problem in receiving the immunizer. The only point of attention in this situation is not having had a fever in the last 48 hours.

Kfouri, however, analyzes that, probably, since the beginning of vaccination, many asymptomatic people with Covid-19 have been vaccinated and that the proposed interval is not a measure with scientific evidence that demonstrated the vaccine would do harm or would necessarily have a performance. different, but rather a precaution.

“The recommendation is based on what is understood of other diseases, on the basis of convalescence [termo que se refere ao período de recuperação que uma pessoa passa após alguma doença]”, he says.

Doctor André Ricardo Ribas Freitas, professor of epidemiology at the São Leopoldo Mandic School of Medicine, explains that the orientation to postpone vaccination after being infected by the virus is related to the production of antibodies during this period.

“On receiving the antigen, the patient’s body begins to produce antibodies to neutralize the virus, and when producing antibodies, the body is learning to defend itself. If the patient already has levels of antibodies high enough to neutralize this virus, the vaccine runs the risk of the vaccine not having an effect”, explains Freitas.

Therefore, he says, the four weeks would be the time needed for the reduction of antibody levels. That way, when the patient receives the injection, their immune system will be prepared to work with new antibodies.

The doctor reinforces that infection with Covid-19 does not guarantee immunization by the disease, so vaccination is necessary to contain the virus.

“The antibodies that are of interest to neutralize the virus are those capable of neutralizing the spike protein. It is not because the virus has more antibodies than the vaccine that the infection is more effective”, he says.