Virus patient data show immune response

PEOPLE who have caught Covid-19, even those with only mild symptoms, are immune from reinfection, at least in the short term, France’s Pasteur Institute has confirmed.

The results follow a study of 160 health workers at two Strasbourg University hospitals who had tested positive for Covid-19 with mild symptoms, none requiring a stay in hospital.

Two types of serology test showed that almost all participants (153 and 159 out of 160 respectively) developed antibodies within 15 days of the start of infection. Another test found that 98 per cent of the patients in whom antibodies were detected were able to neutralise the virus 28 days after first symptoms.

Prof Arnaud Fontanet, who led the study, told France Inter: “We looked for neutralising antibodies that we know provide protection against, say, reinfection. And here, a month later, we found them in 98 per cent of people who had been infected with Sars-cov-2 – results that are indeed good news.”

Until now, data had remained unclear over what proportion of infected individuals developed antibodies.

“The fact they have protective antibodies a month after the start of symptoms suggests that they are very likely to be protected from reinfection if they were exposed once again to the coronavirus,” said Prof Fontanet.

While there was no doubt about the immunity, he said there was a question mark over how long it would last, suggesting it could be “from a few weeks to a few months” in mild cases.

Only 5 per cent of the French population are thought to have been infected, according to findings based on mathematical models and hospital data released by the Pasteur Institute.

Even in the highest-infected “red zones”, such as Paris and eastern France, the rate was barely above 10 per cent – nowhere near the levels required for “herd immunity”.