Covid-19 France: patients still immune a month later

The study, carried out in association with the hospital of Strasbourg, was conducted on 160 volunteers working at the hospital who have had mild forms of the virus and did not need hospitalisation. It found that 159 of them are still immune.

Pasteur Institute professor, Arnaud Fontanet told France Inter: “Antibodies were found in almost all of the patients.”

Antibodies were detected 15 days after the infection, and for 98% of the patients, these protective antibodies were still present after 28 days.

The presence of antibodies was measured by two techniques, a rapid diagnostic test and a test developed by the Institut Pasteur (called S-Flow).

Professor Fontanet added: “We were looking for neutralising antibodies that we know are protective against reinfection for example. And here, after one month, they are found in 98% of people who had been infected with the virus."

Researchers knew that people with severe forms of the disease develop antibodies within 15 days but it was not known what proportion of patients with mild forms of the disease develop antibodies - and if these antibodies were protective - until now.

Having these protective antibodies a month after being infected means people are probably protected against reinfection if they are exposed to the virus again, said Professor Fontanet.

Head of the virology department of Strasbourg hospital, Samira Fafi-Kremer said: “These results are also good news for future vaccine strategies.”

However, it is not known yet how long the protection lasts. Researchers estimate that it can last “from a few weeks to a few months.”

New tests will be done by the institute to determine more on this.