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RIO – Amid the increase in Covid-19 in November, the cases of people who became ill and tested positive for the Sars-CoV-2 coronavirus two months after being considered cured and having negative results stand out. These are cases of possible reinfection and persistence, which may be contributing to the resumption of the growth curve of the pandemic. They turn on the red light for those who thought they were immune and pose challenges to vaccination.
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The fear of reinfection among doctors is real, expressed in internal memoranda, such as the one issued by the Federal Hospital of Lagoa, on November 18. It is impossible, at the moment, to know how many are reinfected. Scientists estimate that if they do not seem to be the norm, they would not be an exception either.
The other four coronaviruses of the common cold, as well as respiratory viruses in general, cause reinfection normally, says virologist from the Federal University of Rio de Janeiro (UFRJ) Clarissa Damaso. Sars-CoV-2 seems to follow the same path.
Reinfections add to crowds and relaxation of measures to contain the pandemic
Before one of the few studies in Brazil that tests the coronavirus with RT-PCR, the gold standard, and monitors professionals in risky activities, such as health and safety, Terezinha Castiñeiras, says that the resumption of growth of Covid-19 cases in Brazil and Europe take place in a curiously coincident period, despite different climatic conditions and pandemic developments.
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Although at this time it is not possible to make any statement, it is a fact that there is a coincidence between the increase in cases and the estimated period for the neutralizing antibodies (those that actually attack the virus) acquired against Sars-CoV-2 to decrease or even disappear.
– With the existing level of knowledge, we cannot say anything. But they are possibilities. The reinfection and also the persistence may be helping to drive the resumption of the growth of Covid-19 registered this month. What is its weight, we do not know – says Castiñeiras, coordinator of the Center for Screening and Diagnosis (CTD) of Covid-19 and head of the Department of Infectious and Parasitic Diseases of the Faculty of Medicine, both of the UFRJ.
To the agglomerations are added reinfections and relaxation of containment and distance measures and personal care (hygiene and use of a mask). The result is seen in the positivity rates.
Rafael Galliez, professor of Infectious and Parasitic Diseases at the UFRJ School of Medicine, says that on November 17 the positive rate in the CTD rose to 37% against 26% in September and 13% in June.
– We do not know the role of reinfections, but they are one more element in an explosive situation, with crowds and more and more people ignoring care – emphasizes Galliez.
The point is that the neutralizing antibodies disappear after a while. One study indicates that they last about six months. But even this is conjecture, emphasizes immunologist Orlando Ferreira, from the Molecular Virology Laboratory (LVM) at UFRJ.
There are other defense mechanisms, of cellular response, which remain poorly understood. Amílcar Tanuri, who coordinates the LVM with Ferreira, points out that people who have had Covid-19 are vulnerable and may not have a favorable genetic makeup to defend themselves against the coronavirus. They lost their defense because it wasn’t very good.
Latin America has the first proven case of reinfection
It is very difficult, at a current technical level, to distinguish what is a second infection from a case of persistence, that is, someone who never got rid of the coronavirus. Although the reports are numerous, it was only this week that the Lancet was published in a scientific journal, the first confirmed case of reinfection in Latin America, that of a 46-year-old Ecuadorian.
To test for reinfection, it is necessary to sequence and compare the viruses from the first and second infection episodes. There must be significant differences in the genome, which would characterize that the person has been infected again. If it’s persistent, the virus that made you sick the first time would have hidden and resurfaced again. None of this is trivial to investigate, explains Ferreira.
As of July there were no suspected cases of reinfection in the CTD, but they have appeared since then.
– Now, some people who tested positive at the beginning of the pandemic and negative, test positive again. Some have high viral loads and this feeds the chain of transmission – says Castiñeiras.
The CTD group already has patients under study. The samples will be sequenced to see if it really is reinfection or persistence. For those who get sick, the suffering is the same. However, for the control of the pandemic it is important to know the ability of Sars-Cov-2 to bypass the immune system, adds Luciana Costa, deputy director of the Institute of Microbiology at UFRJ.
Like other scientists, he points out that having Covid-19 is not a guarantee of immunity. Everyone should take care of themselves. A person who was once vulnerable is still susceptible. As the coronavirus circulates with intensity, it can re-infect the person.
In the case of health professionals, many are also exhausted, exhausted, with low immunity. There can be several triggers.
– People should not fool themselves into thinking that they are protected because they have had Covid-19 or because they have antibodies, since these can be lost and are not the only defense mechanism. If they had Covid-19 it is because they are vulnerable and can have it again – underlines Costa.
Immunity even just with vaccine. Tanuri says that reinfection and persistence are more challenges for vaccination. The vaccines must be strong, have a longer effect, or need more doses.
Clarissa Damaso is confident that vaccines can overcome the problem of reinfection and persistence. She explains that the immunity produced by natural infection is not as strong as that provided by a vaccine.
In natural infection, the body is at a disadvantage because it is already fighting the infection. The vaccine provides defenses before an infection tries to establish itself. In addition, it contains adjuvants and other means to stimulate the immune system.
Damaso does not believe that reinfection is an obstacle to vaccines, but renewals may be necessary, as is already the case with the flu. And while the vaccine does not arrive, follow the usual care:
– Everyone should wear a mask, hygiene and keep their distance – emphasizes Dámaso.
