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Coronavirus (Photo: Getty Images)
Asymptomatic and even mild cases of covid-19 do not offer immunization against the disease, according to a new Fiocruz study published on Wednesday (12/23). Posted in Social Science Research Network, work reinforces the idea that re-infection by SarsCov2 is possible and can result in serious illness. In other words, the population is even more vulnerable to the pandemic than previously thought.
The lead author of the study, virologist Thiago Moreno, said that he accelerated the dissemination of the results to the maximum due to a social responsibility issue. vacation and vacation travel. “If you have ever had an asymptomatic or mild infection, it does not mean that you will not have it again, or that it will be mild again.”
The study was carried out at the Center for Technological Development in Health (CDTS / Fiocruz) based on the sequencing of genotypes of the new coronavirus. The study followed four people weekly who had not shown any symptoms since the start of the pandemic in March. Serological tests and RT-PCR were performed on all the subjects followed and all were positive, although they were asymptomatic.
By sequencing the genomes, the researchers confirmed that one person contracted the virus associated with an imported genome and another had a viral structure associated with the genome already circulating in Rio de Janeiro. According to Moreno, one of the volunteers returned to look for the research group. in late May, citing stronger signs and symptoms of covid-19, such as fever and loss of taste and smell. “
When we did the RT-PCR again, all four subjects tested positive. What we observed was a reinfection within the family environment, “the researcher explained.” However, the person who presented the genotype associated with imported cases in March was now infected by another strain. The other individual, who had been infected with the genotype circulating in Rio, remained with the same genotype, but already had some accumulated mutations, which allowed us to interpret that it was a reinfection and not a persistence of the infection ”.
For the virologist, the work reinforced the notion that reinfection is possible, something common among respiratory viruses. According to him, the first exposure to the virus did not guarantee an immune memory of the organism. “People with asymptomatic or very mild cases, if they are re-exposed to the virus, they can get an infection again,” he said. “This time, it may be a more serious infection than the first, as research shows.”
When the organism is invaded by some foreign microorganism, it initially launches a generic response to combat the invader. Since this response is not specific, it does not generate a memory of the invasion, although it does manage to overcome the milder forms of infection. In these cases there is no immunization, in the most serious and prolonged forms of the disease it is different.
There is the formation of a specific adaptive response to combat this invader. That answer is what makes up immunization. Another problem, according to Moreno, is that in some cases an immunization can occur, but it is not lasting, this is what happens in the case of the influenza virus, for example. “The two mechanisms may be happening in parallel,” he explained.
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