A preprint (not a published paper), uploaded to medRxiv, has described a case study of COVID-19 infection on a fishing boat where some people on board had pre-existing COVID antibodies.
Prof John Edmunds, Professor in the Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene & Tropical Medicine, said:
“This is a very significant finding. It suggests that neutralising antibodies (antibodies that prevent SARS-CoV-2 from entering host cells) can protect against infection. This has not been previously demonstrated in humans.
“The numbers are small and we don’t know how long any protection might last, so some caution needs to be applied. However, if these results are confirmed and backed up by similar studies, then it opens up the possibility of allowing people who have neutralising antibodies to start to return to normality with some degree of safety. It is also very good news for vaccine development as if a vaccine induces neutralising antibodies then it implies that it might be protective.”
Prof Martin Hibberd, Professor of Emerging Infectious Disease at the London School of Hygiene and Tropical Medicine, said:
“This is a nice study, suggesting that pre-immunity -but not pre-exposure gives you resistance to re-infection; but the numbers of people are small. They state that 3 crew members with high levels of antibody and evidence of having neutralizing antibody, were resistant to infection, whereas 3 crew members with low levels of antibody and no evidence of neutralizing antibody were re-infected, along with 85% of the rest of the crew. This suggests that having antibodies alone, is only 50% predictive of resistance, although higher antibody levels were correlated with neutralising antibodies. However, they do not know when these 6 crew members were infected, so the level of antibody (and virus neutralization) could be related to the time since infection. Potentially, higher antibody titres could suggest more recent infection and more protection.
“The small numbers of people investigated make this study hard to interpret fully and I suspect that more conclusive studies will be coming soon, perhaps from the large-scale vaccine phase 3 trials that are being done now.”
Prof Danny Altmann, Professor of Immunology at Imperial College London, said:
“While this is a small study, it offers a remarkable, real-life, human experiment at a time when we’ve been short of hard-line, formal, proof that neutralising antibodies genuinely offer protection from re-infection, as predicted by animal models. In short, its good news. Who knew immunology research on fishing boats could be so informative?”
Prof Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said:
“Whilst the number of patients who tested antibody positive before the ship left dock was low, the fact that the three with detectable virus neutralising antibodies were not infected, whilst the three without neutralising antibodies – as well as the majority of the people lacking any detectable antibodies – before departure became infected is really interesting. This suggests that individuals who have had a prior exposure to virus are susceptible to reinfection unless they have appreciable levels of neutralising antibodies. This gives us important insight into the type of immunity that might protect from future infection. What it doesn’t tell use is whether or not past exposure can protect against serious disease in those people lacking detectable neutralising antibodies. Both are relevant to vaccine design.”