A new study in France found that even the most mild cases of COVID-19 infection can give rise to protective antibodies, sometimes weeks after symptoms have subsided.
The findings were jointly published on the site MedrXiv.org by the Pasteur Institut and Strasbourg University Hospitals, both in France.
"The results of the study are very encouraging for those who have been infected by the virus," said Samira Fafi-Kremer, the study's lead author and head of virology at the Strasbourg University Hospitals.
The results provide a way forward in the understanding of the immune response of the virus, although they must now be peer reviewed as it is the standard methodology.
The path of the study emanated from the Strasbourg region, which lies in eastern France, one of the hardest-hit by the virus.
After a mid-February evangelical gathering in Mulhouse, numerous health care workers then at the nearby Strasbourg hospitals became infected with the coronavirus a few weeks later.
Blood samples from 160 of those staff were then analyzed. The samples were taken from those workers who were not hospitalized, thus had more mild cases of the virus.
Rapid diagnostic tests found antibodies in 153 samples; more complicated S-Flow tests found antibodies in 159.
Since antibodies had been found in all but one of the subjects, researchers found that the neutralizing activity of antibodies increased over time. More testing will be needed to find out their lasting effect.
Fafi-Kremer is encouraged by the results.
"Even those who develop mild cases of COVID-19 are capable of producing antibodies that remain present at least 40 days after the appearance of symptoms. It remains to be determined how long they last," she said.