On August 24, a press release was leaked (before the scientific study was published) aboutthe first documented case of reinfection by SARS-CoV-2, which causes COVID-19, in a 33-year-old man(without any immune deficiency) in the city of Hong Kong.
In March, this patient suffered from the disease (positive CRP) with symptoms and was hospitalized. He was discharged in April with a negative PCR. But in August he gave positive PCR again,this time, no symptoms.
What is worrying about the case is that the genetic material of the virus that infected him in March and in August belongs to two different strains, as the researchers published in the study, accepted on August 25 by the journalClinical Infectious Diseases.
These were the authors’ conclusions:“Epidemiological, clinical, serological and genomic analyzes confirmed that the patient had a reinfection rather than a persistent viral shed from the first infection. Our results suggest that SARS-CoV-2 may continue to circulate among human populations despite herd immunity due to natural infection or vaccination. More studies of reinfected patients will shed light on important protective correlates for vaccine design. “
This case (for the moment, isolated) can give us some indication about how immunity works, and has also raised doubts in the population about whether the vaccines will be viable, since the virus could mutate to ‘escape’ such immunity. Of course, we must still be prudent before jumping to conclusions. The WebScience Media Centrehas collected the opinion of several international experts on this case of reinfection.What clues does this case offer us about immunity against this coronavirus?
Dr Paul Hunter, professor of medicine at the Norwich School of Medicine at the University of East Anglia, believes that the fact that the March and August virus strains are genetically different “shouldn’t be too surprising.”
The first thing Dr. Hunter points out is that the intensity of the antibody response is different between people with severe or mild disease. This means that ” people with a mild illness are likely to have a shorter duration of immunity than those with a severe illness.”
Being a young person, this probably means that he had a mild illness and therefore would be expected to have a shorter duration of immunity ”.
On the other hand, Hunter points out that the implications of this case should not be exaggerated: “It is very likely that subsequent infections do not cause an illness as severe as the first episode due to some degree of residual immunity that may not be sufficient to stop the infection. , but yes to reduce the risk of serious illness ”.
Nor is it yet clear how likely this person is to pose a risk to others.
Unknowns
Dr. Jonathan Stoye, Group Leader of the Retrovirus-Host Interactions Laboratory at the Francis Crick Institute, highlights three critical unknowns regarding SARS-CoV-2 infection:
“Does infection always lead to a protective immune response? If the answer to the first question is yes, how long does immunity last? Can the virus change (mutate) to escape an initial immune response? “
“Reactivity to the first virus, but not the second, could suggest mutation of the virus to escape immune responses,” he adds.
Does this mean that the vaccines we are developing are useless?
Hunter remains cautious: “This report is not necessarily an indication that immunization may not be effective. We need more information on this case and other cases of reinfection before we can really understand the implications. “
For his part, Professor Brendan Wren, professor of microbial pathogenesis at the London School of Hygiene and Tropical Medicine, stated the following: “ It is expected that the virus will mutate naturally over time . This is a very rare example of reinfection and should not negate the global drive to develop COVID-19 vaccines, “he concludes.
The case of reinfection, in fact, could further accentuate the need to obtain immunity through vaccines, because vaccines boost the immune system, thus providing stronger protection.
However, other experts are not so optimistic. Dr David Strain, Senior Clinical Professor at the University of Exeter and Chairman of the British Medical Association’s Medical Academic Staff Committee, points out that reinfection is a concerning finding for several reasons: “The first is that it suggests that an infection previous does not protect. The second is that it raises the possibility that vaccines may not provide the hope we have been hoping for. Vaccines work by simulating an infection, allowing the body to develop antibodies. “
“If the antibodies do not provide lasting protection, we will have to return to a strategy of near viral elimination to return to a more normal life,” he concludes.
References:
Science Media Center
Kelvin Kai-Wang To et al. ‘COVID-19 re-infection by a phylogenetically distinct SARS-coronavirus-2 strain confirmed by whole genome sequencing’. August 25, 2020. Clinical Infectious Diseases, ciaa1275, https://doi.org/10.1093/cid/ciaa1275
