THE ESSENTIAL
- Despite the effectiveness of RNA vaccines in protecting once morest severe COVID-19 pneumonia, some severe cases have been reported worldwide.
- These cases are thought to be due to a poor antibody response to the vaccine in people at risk, such as the elderly.
These are very rare cases but raise questions. Indeed, some people develop severe forms of Covid-19 despite a two-dose vaccination, and even though this vaccination has allowed the production of antibodies to SARS-CoV-2.
48 cas
This issue was the subject of an international study, led by a French team of researchers, and published last June in the journal Science Immunology.
For their work, the researchers looked at 48 cases of severe forms of the disease developed by 34 men and 14 women, aged 20 to 86, yet all vaccinated once morest the virus, and infected with the Delta variant of Covid- 19. All had been admitted to intensive care following their infection.
Antibody
The primary objective was to ensure that the vaccine had worked correctly in these patients. However, in six patients, vaccination had not made it possible to provide them with neutralizing antibodies, either because they were taking immunosuppressive treatments, or because they were infected with HIV or were being treated for lymphoma. They were therefore excluded from this study.
Concerning the 42 remaining patients, the researchers noted the presence of an antibody which attacks certain molecules of our immune system making it possible to fight once morest the virus, called “type 1 interferons” (IFN-1).
line of defense
Indeed, in 10 of the 42 patients, these “auto-antibodies” – present in their body long before they were infected with the virus – prevent the IFN-1 from acting correctly.
“Because of these auto-antibodies, these patients cannot oppose a rapid line of defense once morest SARS-CoV-2 via interferons, explains Paul Bastard, one of the signatories of the study, to the Monde. Lacking this first defense, the virus multiplies too quickly. The anti-Covid-19 antibodies induced by vaccination arrive too late: they fail to neutralize the virus.
Paul Bastard believes that it would be useful to track down these “auto-antibodies” in immunocompromised people. “The percentage of people with these auto-antibodies increases a lot with age: less than 1% among those under 65, it exceeds 4% among 80-85 year olds”concludes the researcher.
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