Omicron variant: Vaccination reveals a strong but incomplete immune escape. A study signed by Matthieu Mahévas’ group within the France Pirenne team and published this month in Immunity

The Omicron variant of SARS-CoV-2 can escape neutralization by vaccine-induced antibodies as well as by antibodies from convalescent plasma. Memory B cells (MBs) represent a protective bulwark against SARS-CoV-2 because they persist after infection and vaccination enhances their affinity. The ability of BMs, generated by mRNA vaccines, to recognize the Omicron variant remains unknown to date.

Matthieu Mahevas’ group, associated with several teams from the Institut-Necker and the Institut Pasteur, evaluated the affinity and neutralizing power against the Omicron variant of several hundred monoclonal IgG antibodies derived from BMs from individuals vaccinated against COVID-19, whether they were cured or naive.

Compared to other variants, Omicron escaped recognition by a higher proportion of BM-derived antibodies and only 30% of them retained high affinity to the Omicron RBD domain, the reduction in neutralizing power was even more pronounced. Nevertheless, neutralizing clones could be found in all individuals analyzed.

Therefore, despite the high potential for immune escape of the Omicron variant, these results suggest that the memory B-cell repertoire generated by mRNA vaccination still provides protection against severe forms of COVID-19. Access to the article