Three crew members of a Seattle fishing boat who had antibodies capable of neutralizing the coronavirus were not re-infected during a COVID-19 outbreak that struck the majority of people on board, study finds .
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“The presence of neutralizing antibodies from a previous infection was significantly associated with protection against reinfection,” conclude researchers from the University of Washington and the Fred Hutchinson Cancer Research Center in Seattle.
This small study, which appeared on the prepublication site medRxiv and not in a peer-reviewed journal, is one of the first to suggest a link between neutralizing antibodies – those that prevent the virus from attaching to cells – and protection against infection in humans.
Out of 122 people, 120 were tested before boarding the fishing boat in May, for both the presence of the active virus (virological test) and antibodies in the blood (serological test) indicating a previous infection.
None of the crew members were tested positive for the virus by then, but six had contracted it before and therefore had antibodies in their blood.
Upon returning from the boat, a large majority of the crew members (85.2%) had been infected with the virus, including three of those who had antibodies in their blood before departure. But those who remained unharmed had proven neutralizing antibodies.
As for the other three, the fact that they were re-infected could be explained by the fact that their first infection, mild or asymptomatic, resulted in ephemeral production of antibodies or at a level too low to protect them. The researchers also do not rule out the possibility that the first serological result is a “false positive”.
For Jonathan Ball, professor of molecular virology at the University of Nottingham, who was not involved in the study, “this suggests that people who have previously been exposed to the virus are likely to re-infect themselves unless they are not. ‘have appreciable levels of neutralizing antibodies’.
“This gives us important insight into the kind of immunity that might protect against future infection,” but it doesn’t show, he says, whether or not past exposure may or may not protect against serious illness in people lacking antibodies. detectable neutralizers.
“This is a very important discovery,” says Professor John Edmunds of the London School of Hygiene & Tropical Medicine.
“This suggests that neutralizing antibodies may protect against infection,” which had not been shown previously in humans.
But for his colleague Professor Martin Hibberd, a specialist in emerging infectious diseases, “the small number of people studied makes this study difficult to fully interpret”, and more conclusive studies should be available soon, “perhaps from the trials of phase 3 of large-scale vaccines which are underway ”.