Omicron Variant Shows Serious Decrease In Neutralizing Activity, Lab Studies Show

Purple pipette doing sample work in a lab
A slew of laboratory studies on the omicron variant of COVID-19 show significantly impaired neutralizing titers (a measure of antibodies in one’s blood) from the available vaccines, worrying some experts that the variant may pose a challenge to available forms of immunity. Photo by Louis Reed on Unsplash

Laboratory studies of the omicron variant of COVID-19 from multiple sources reveal a dramatic decrease in neutralizing activity from prior infection with earlier variants and the available vaccines. The results provide a challenging prospect for the future of the pandemic if the variant becomes dominant, and strongly encourage a booster dose for all adults, regardless of health conditions.

One important caveat is necessary: neutralizing activity, the kind the available studies are examining, do not directly translate to vaccine effectiveness. While the data raise concerning questions about the ability of omicron to evade parts of the immune response that vaccination and prior infection generate, they cannot be perfectly mapped onto vaccine effectiveness as a percentage.

Dr. Alex Sigal of the Africa Health Research Institute released data showing a severe reduction in antibody response to the new variant. “There is a very large drop in neutralization of Omicron by BNT162b2 immunity relative to ancestral virus,” Sigal summarized on social media.

However, as research shows omicron continues to use the ACE2 receptor, the same pathway that earlier variants have used, Sigal was optimistic about the possible meaning his team’s research pointed to for vaccine effectiveness. “This was better than I expected of Omicron,” Sigal wrote. “The fact that it still needs the ACE2 receptor and that escape is incomplete means (it is) a tractable problem with the tools we got.”


Analysis of Sigal’s data suggests that the previous standard for full vaccination—two doses of either Pfizer or Moderna’s mRNA vaccine—may be insufficient to prevent transmission of the omicron variant. But some experts interpreted Sigal’s data to suggest that the booster’s powerful replenishment of neutralizing antibodies would extend its effectiveness against the new variant of the virus.

Model of a coronavirus
Results showing a reduction in neutralizing activity are now available from several independent studies and data from Pfizer-BioNTech itself. Photo by Fusion Medical Animation on Unsplash

Data from Dr. Sandra Ciesek, director of the Institute of Medical Virology at the Universitätsklinikum Frankfurt, paint a more concerning picture. Ciesek’s research includes two conclusions. The first is a severe elimination of neutralizing titers (a measure of antibodies in one’s blood) for those who were previously considered “fully vaccinated,” meaning two doses of Pfizer or Moderna or a dose of AstraZeneca plus one mRNA shot.

But the data also examined the results compared to three shots of Pfizer—a booster dose—revealing 25% neutralizing titers only three months after the booster. This represents “up to 37 times the reduction in delta vs. omicron,” Ciesek wrote on social media.

Pfizer and BioNTech’s own data, which examined neutralizing activity only one month after boosting, showed meaningful neutralizing activity against the omicron variant. BioNTech’s co-founder and CEO, Dr. Ugur Sahin, summarized the companies’ joint results. “Our preliminary, first dataset indicate that a third dose could still offer a sufficient level of protection from disease of any severity caused by the omicron variant.”

Results are still preliminary, and among the several laboratory studies, which vary in methods and comparative samples, there is some contradictory evidence for what this means for the vaccines’ protection against transmission.

Most importantly, the studies are not examining the body’s response to the virus beyond infection. “These data cannot say anything about whether you are still protected against a severe course (keyword T cells),” Ciesek explained.

Experts have consistently found t-cell response to be more durable against viral infections than antibodies, leaving strong hope that in spite of omicron’s evasiveness, vaccinated individuals will maintain their resistance to hospitalization and death.

Continued expert analysis of the studies as well as additional information from the researchers responsible for the data are needed to make concrete assumptions about the future of the pandemic.

What is clear from the data available is that omicron does possess the antibody resistance that observers feared it would, and that the most significant levels of neutralizing activity are found in those with three shots, or hybrid immunity, meaning prior infection followed by two shots.

While the original vaccine formulation in the form of a booster proved more than enough to extend robust and lasting protection against delta, some researchers now conclude that a specific omicron booster is a worthy goal. “The data confirm that developing a vaccine adapted for omicron makes sense,” Ciesek wrote.

Pfizer-BioNTech’s joint release asserted that an omicron-specific booster was in development. “The companies continue to advance the development of a variant-specific vaccine for Omicron and expect to have it available by March in the event that an adaption is needed to further increase the level and duration of protection,” the release read.

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