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Vax Facts: Study shows how quickly vaccines wane against omicron

A new study shows the effectiveness of two-dose mRNA vaccines falls sharply in six months, but a third dose restores protection longer against omicron.

GOLDEN VALLEY, Minn. — A new, massive study shows just how quickly COVID-19 vaccines lose their potency against the omicron variant of the coronavirus, and why booster shots are essential for extending protection. 

The study, published last week in the New England Journal of Medicine, involved more than 2 million people and showed macro-scale data on how well and how long each vaccine fought off symptomatic omicron infections.

After two shots of the Pfizer vaccine, protection against symptomatic omicron infections went from 65 percent in the first month following vaccination, down to just 8 percent in six months.

Moderna went from 71 percent initially, down to 15 percent six months later.

After an mRNA booster of either brand, protection popped right back up to or above initial vaccine levels. The results showed the protection after the booster shot appeared to last longer than just a two-shot regiment.

Dr. Abinash Virk, infectious disease specialist at Mayo Clinic, says if you have not received your booster shot, meaning the third shot of one of the mRNA vaccines, you should still get it.

“So I would still say yes, even if you got omicron, go ahead and get boosted because it will get you additional protection,” said Dr. Virk.

Dr. Virk says an omicron-specific booster is in the works, but it's unclear if it would have any advantage over existing shots. Because of that, she advises the roughly half of booster-eligible Americans who have not received a third shot not to wait.

Currently, the Centers for Disease Control and Prevention does not recommend any additional boosters, except for severely immunocompromised people. The CDC does recommend a fourth shot for those in that category.

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