Covid-19: patients can be immunized one month after infection

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A study by the Pasteur Institute and the CHU in Strasbourg indicates that the vast majority of patients with a minor form of Covid-19 disease develop neutralizing antibodies up to 28 days after infection.

Are former Covid-19 patients immunized against the coronavirus? This is one of the most important questions that affects scientists. On Tuesday, May 26, the CHU Strasbourg and the Pasteur Institute provided initial responses in a preliminary study published on the MedRxiv platform.

The researchers studied 160 volunteer caregivers, infected with SARS-CoV-2 and diagnosed positive by PCR testing. They all work in university hospitals in Strasbourg and have developed minor forms of the disease that do not require hospitalization.

In a press release, the Pasteur Institute said that most of them had developed antibodies within 15 days of the start of their infection. Antibodies, which could give them immunity "for several weeks". For 98% of patients, neutralizing antibodies were detected after 28 days. Results "encouraging", since little is known about the immunity mechanisms against the new coronavirus.

Serological tests, performed after PCR diagnosis, have allowed researchers to discover that the neutralizing activity of the antibodies increases over time, "suggesting that people develop potentially protective immunity."

"People with severe forms of the disease were known to develop antibodies within 15 days of the onset of signs. We now know that this is also true for those who develop minor forms, even if the antibody rates are likely higher. weak, "explains Arnaud Fontanet, co-author of the study and head of the Global Health department at the Pasteur Institute in France.

Persistent immunity?

It remains to be seen how long this immunity can last. "Our study shows that antibody levels are, in most cases, compatible with protection against reinfection with SARS-CoV-2, at least up to 40 days after the onset of signs," added Timothée Bruel and Olivier Schwartz, respectively researcher and head of the Virus and Immunity Unit of the Pasteur Institute.

However, the encouraging results are preliminary results and more tests are still needed to determine whether or not immunity persists over time. "The goal now is to assess the long-term persistence of the antibody response and its associated neutralization capacity in these health workers," the experts conclude.

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