A healthy young woman who developed antibodies against the new coronavirus (Covid-19) after being infected in the first wave of the pandemic was reinfected in September, De Standaard newspaper reported on Saturday, based on a Belgian case study that is still to undergo a peer review.
This could indicate that the number of antibodies drops relatively quickly after infection, virologist Kevin Ariën of Antwerp’s Institute of Tropical Medicine (ITG) commented.
This is probably the first documented case in the world in which it had been noted that the infected person’s immune system had been intact, and their immune response had been good, after a first infection.
“In previous reinfection cases, the immune response had not been measured or was not fully functional,” Ariën said. “This case makes one think, in any event, of the other coronaviruses, whether SARS or MERS. There, too, we saw immunity drop quickly below a ‘critical threshold.’”
The re-infected woman is a nurse’s aid at a Belgian hospital. She still had antibodies when she was re-infected, but they had apparently not been enough.
“Either the fact that she had antibodies was not enough, or their number had fallen below that critical threshold,” the ITG virologist explained.
This case study could prove very important. On one hand, it could serve as an argument against herd immunity. On the other hand, it could be necessary to take it into account in vaccine research since it could indicate that a vaccine that provides very good protection against Covid-19 would not be able to do so for extended periods.