Early data suggests the omicron variant may be better able to evade vaccine antibodies than other variants. But several infectious disease experts caution that these findings don't provide a complete picture of omicron's ability to escape vaccine-induced immunity, and that vaccinated people will likely remain protected against severe outcomes.

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Omicron may evade vaccine antibodies, early data suggests

Several laboratory studies from around the world suggest that the omicron variant may more easily evade neutralizing antibodies produced by the Pfizer-BioNTech Covid-19 vaccine.

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For example, South African researchers found a 41-fold drop in antibody neutralization against omicron compared to an earlier variant, and a German study found a 37-fold reduction in antibody neutralization against omicron compared to delta.

Similarly, data from Pfizer and BioNTech found that individuals who had received two doses of their vaccine had a 25-fold reduction in neutralizing antibodies. According to the companies, this finding suggests that two doses alone "may not be sufficient to protect against infection" from omicron.

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However, several infectious disease experts caution that studying omicron's ability to evade neutralizing antibodies doesn't provide a complete picture of the variant's ability to infect people, or of how severely it could affect those it does infect.

For instance, Alex Sigal, the virologist who led the South African study, said while laboratory tests show a significant reduction in antibody effectiveness against omicron, this doesn't necessarily mean that the variant will escape vaccine-induced immunity in real life. "The vaccine takes a hit, but it not a completely different ballgame," Sigal said. "The escape of this variant is robust, it's extensive. But it's not complete."

In addition, according to The Atlantic, laboratory studies conducted so far have focused on the effectiveness of neutralizing antibodies, which comprise just one part of the body's extensive immune system defenses. In addition to these antibodies, there are also T cells and B cells, which experts say offer more robust protection against coronavirus variants.

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For instance, Lisa Gralinski, a coronavirologist at the University of North Carolina at Chapel Hill, said the mutations that allow variants like omicron to evade antibodies are not likely able to bypass T cells. Pfizer and BioNTech also shared a similar sentiment, saying that "vaccinated individuals may still be protected against severe forms of [Covid-19]" even if neutralizing antibodies are diminished for those with only two doses of their vaccine.

Further, Deepta Bhattacharya, an immunologist at the University of Arizona, said even in a scenario where protection against both infection and mild illness from omicron significantly decrease, vaccine immunity against severe Covid-19 probably won't experience more than "a small drop."

Ultimately, according to Jeremy Faust, an emergency medicine physician at Brigham and Women's Hospital, omicron's antibody evasion "should primarily alarm the unvaccinated, especially adults. As delta did, omicron will mostly punish the unvaccinated." He added that boosters will likely be needed for older individuals and those who are immunocompromised to offer maximum protection against severe disease.

Infectious disease experts told The Atlantic and STAT News that current information about the omicron variant is still preliminary. Moreover, experts said that more real-world data, including on breakthrough infections and whether omicron will outcompete the delta variant, is needed to determine omicron's actual impact on vaccine immunity.

"Extrapolating from … lab assays to what happens clinically is uncertain. What remains the most important indicator [of] how serious a threat omicron poses to fully vaccinated people will come from hospitalization data in the coming weeks," said John Moore, an immunologist at Weill Cornell Medicine. (Faust, Inside Medicine, 12/8; Wu, The Atlantic, 12/8; Joseph, STAT News, 12/3)