A study, supported by the European Unions Health Emergency Preparedness and Response Authority (HERA), was conducted to determine the efficacy of therapeutic antibodies and the antibodies developed in individuals previously infected with COVID-19 or vaccinated people, in neutralizing the Omicron variant.

Scientists assessed the sensitivity of Omicron to antibodies compared with the Delta variant. They tested nine monoclonal antibodies currently being used in clinical practice or under preclinical development. Six antibodies were found to lose all antiviral activity, while the other three were 3- to 80-fold less effective against Omicron compared to Delta. The antibodies Bamlanivimab/Etesevimab, Casirivimab/Imdevimab, and Regdanvimab did not have any antiviral effect against Omicron variant. Tixagevimab/Cilgavimab appeared to be 80 times less effective against Omicron compared to Delta.

The blood of patients who had previously been infected with COVID-19, obtained up to 12 months after symptoms, and that of people who had been given two doses of a COVID-19 vaccine, obtained five months after vaccination, could hardly neutralize the new variant. The sera of individuals who had been administered a booster dose of Pfizer vaccine, assessed one month post-vaccination, was found to be effective against Omicron. However, in cell culture assays, 5 to 31 times more antibodies were needed to neutralize the new variant, compared to Delta… (ET Healthworld – ANI, January 11, 2022)