Two doses of the Moderna COVID-19 vaccine may be less effective at stopping the omicron variant, according to new research.

The study — which has not been peer-reviewed — analyzed 30 blood samples from patients who were double vaccinated with two Moderna shots, according to The Hill. Researchers then tested the vaccine against a pseudovirus version of the omicron strain.

  • Scientists found antibodies from two Moderna shots were 50% less effective at stopping the omicron strain.
  • This “could lead to an increased risk of symptomatic breakthrough infections,” the researchers said, per The Hill.
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However, 12 participants who received a Moderna booster shot had a 12-fold improvement in stopping omicron, as the booster reduced the risk of the new variant.

So far, research suggests the omicron variant causes less severe symptoms among vaccinated infected patients. Per The Washington Post, a new study found the variant can evade vaccines, but will often cause mild symptoms when it does.

Experts are still worried about the variant’s potential spread, even to those who are vaccinated.

  • “Even if it causes only mild disease — and that’s far from certain — that could still mean many people end up in the hospital and dying,” according to CNN.

That’s why Dr. Anthony Fauci, the White House medical adviser on the coronavirus, said booster shots are wildly important to staying safe from omicron, per CNBC.

  • “Our booster vaccine regimens work against omicron,” Fauci said at a White House COVID-19 update Wednesday. “At this point, there is no need for a variant-specific booster.”