There is an alarming number of changes in the virus’s spike protein that could pose a threat to the effectiveness of current vaccines and therapeutic antibodies.
The new study tested the ability of antibodies generated by vaccination to neutralize the omicron variant in laboratory assays that pitted antibodies against live viruses and against pseudoviruses constructed in the lab to mimic omicron.
Antibodies from people double-vaccinated with the four most widely used vaccines were significantly less effective at neutralizing the omicron variant than the ancestral virus. Antibodies from previously infected individuals were even less likely to neutralize omicron.
Individuals who received a booster shot of either of the two mRNA vaccines are likely to be better protected, although even their antibodies exhibited diminished neutralizing activity against omicron.
“The new results suggest that previously infected individuals and fully vaccinated individuals are at risk for infection with the omicron variant,” says Ho. “Even a third booster shot may not adequately protect against omicron infection, but of course it is advisable to get one, as you’ll still benefit from some immunity.”
The results are consistent with other neutralization studies and early epidemiological data from South Africa and the U.K., which show the efficacy of two doses of the vaccines against symptomatic disease is significantly reduced against the omicron variant.
The new study suggests that all therapies currently in use and most in development are much less effective against omicron if they work at all.
In neutralization studies with monoclonal antibodies, only one (Brii198 approved in China) maintained notable activity against omicron. A minor form of omicron is completely resistant to all antibodies in clinical use today. The authors note that omicron is now the most complete “escapee” from neutralization that scientists have seen.
In this study, Ho’s lab also identified four new spike mutations in omicron that help the virus evade antibodies. This information should inform the design of new approaches to combat the new variant.
Ho suggests that scientists will need to develop vaccines and treatments that can better anticipate how the virus is evolving.
It is not too far-fetched to think that SARS-CoV-2 is now only a mutation or two away from being entirely resistant for current antibodies, either the monoclonal antibodies used as therapies or the antibodies generated by vaccination or infection with previous variants,” says Ho.
Source: Medindia
