The study is published on the bioRxiv portal of scientific research and has yet to be reviewed by peers.
"Following the 2nd dose, we observed a 30-fold reduction in neutralizing activity against the omicron variant. Through six months after the 2nd dose, none of the sera from naive vaccinated subjects showed neutralizing activity against the Omicron variant," the abstract read.
According to the study, after the second dose, the neutralizing activity of antibodies was reduced by 30 times amid contact with the Omicron variant, compared with other strains.
However, after a booster shot, the indicators reduced by only 14 times. Moreover, the third dose provided protection from the Omicron strain for over 90% of boosted subjects.
"These findings show that a 3rd dose is required to provide robust neutralizing antibody responses against the Omicron variant," the scientists said.
Omicron was first detected in South Africa in late November. The World Health Organization designated it a "variant of concern" due to exceptionally high number of mutations. Despite the new wave of travel bans on Africa, the new variant has since been detected in Europe, Asia, and the Americas.