Study identified cases in four professionals at the Hospital de Clínicas da Unicamp. Research is conducted by the Emerging Virus Studies Laboratory
A survey carried out by the Laboratory for Studies of Emerging Viruses (LEVE), at the Institute of Biology (IB) at Unicamp, identified four cases of reinfection by SARS-CoV-2 in healthcare professionals at the Hospital de Clínicas (HC). What draws researchers' attention is that the viruses found in patient samples do not correspond to the so-called variants of concern, VOCs (Variants of Concern), the most common types of SARS-CoV-2 identified in cases of reinfection. The discovery opens the way for investigations into the characteristics of the immune response produced in the body following coronavirus infection and vaccines, in addition to highlighting the importance of protective measures. The study was published in the journal Emerging Infectious Diseases, from the Centers for Disease Control and Prevention (CDC) in the United States.
The cases occurred in three nurses and one HC employee, with an average age of around 44 years. The first coronavirus infections were recorded between April 5 and May 10, 2020, with contamination by the B lineage of SARS-CoV-2, the first to circulate in Brazil at the beginning of the pandemic. There were no complications in any of the cases and all recovered within 10 to 23 days. With the emergence of new symptoms of Covid-19, it was necessary to confirm whether the cases met the requirements to be characterized as reinfections.
"Our first question was: are these patients, who present cases of Covid-19 for the second time, cases of reinfection or is it a persistent viral infection, that is, the virus has not left the person?", comments José Luiz Módena, IB teacher and LEVE coordinator. He explains that in cases of reinfection, patients test positive for SARS-CoV-2 again after at least 45 days of the first infection, with negative laboratory tests between the two positive events. In the case of the four patients, the second infections occurred within 55 to 120 days of the first.
After sequencing and comparing the samples collected in the two episodes of infections, the surprise was that the viruses found in the second episodes were from strains very similar to those identified in the first cases. Módena explains that cases of reinfection with SARS-CoV-2 are not common, but the trend that has been recorded among researchers is that, when they do occur, they are as a result of infection with variants of concern. These are cases of SARS-CoV-2 strains that present a significant number of mutations that can alter the structure of the virus's surface proteins, called spikes, which can facilitate entry into the body's cells, making it more transmissible, or still escaping the antibodies produced as a result of previous infections caused by SARS-CoV-2. Currently, the documented variants that cause the most concern in the world, due to their effects, are those from Manaus (P1), the United Kingdom (B1.1.7) and South Africa (B1.351).
The cases of reinfection documented among HC professionals therefore draw attention because it was not expected that the virus would escape the patients' immune response precisely because they did not present significant mutations in the spike proteins. According to Módena, one of the hypotheses for this to have occurred is that, as they are on the front line of the fight against Covid-19, they are more exposed to contamination.
Vaccines remain safe and care remains necessary
Although they do not present significant changes that determine them as new variants or lineages of SARS-CoV-2, the professor highlights that in three of the four cases a point mutation in the spike protein was identified, which is not described as a factor of concern, but which It has been observed in research documenting positive cases of Covid-19 in people who have already been vaccinated. "It could be a mutation that went unnoticed, that no one ever paid attention to, but that could now be involved in cases of immune escape", he comments.
However, this does not make coronavirus vaccines any less safe or efficient, as the body's immune response is not restricted to the production and action of antibodies. "We are trying to characterize the potential of the virus to continue circulating even in people who have been vaccinated. But that doesn't mean that the vaccine doesn't work, or that it isn't effective, or even that infection with SARS-CoV-2 doesn't give any type of protection for a second infection. We are looking at one arm of the defense, which are antibodies, and at just one of their functions, which is their ability to neutralize viruses", he explains.
What Módena warns is that even people who have already been vaccinated need to maintain precautions such as social distancing, wearing masks and hand hygiene, as vaccines protect against the development of Covid-19, but do not prevent the transmission of the virus: "If people who have been vaccinated start going out, no longer wearing masks, not taking any precautions, they can cause these viruses to continue to be transmitted. This process of transmission between vaccinated and unvaccinated people, combined with the rate of mutations of the virus , it could lead to the emergence of a virus that actually escapes the protection of vaccines and causes disease, and that's what we don't want."
The full study can be accessed at https://wwwnc.cdc.gov/eid/article/27/6/21-0558_article