Most American children won't be fully vaccinated by Christmas — but the kid-sized Covid vaccines can still make your holiday gatherings a lot safer, according to one Harvard epidemiologist.

"Vaccinate," Dr. Michael Mina, an assistant professor of epidemiology at the Harvard T.H. Chan School of Public Health, tweeted on Sunday. "Even a single dose for your kid 10 days prior is an incredible safeguard."

Kids ages 5 to 11 have been eligible for reduced doses of Pfizer's Covid vaccine since Nov. 2. The vaccine requires two shots given 21 days apart, and people are considered "fully vaccinated" two weeks after receiving their second dose, according to the Centers for Disease Control and Prevention.

So, even if your children got their first doses on their first day of eligibility, they wouldn't be fully vaccinated until Dec. 7 — before Christmas, but well after Thanksgiving and barely missing the end of year's Hanukkah on Dec. 6.

That doesn't mean you should delay your children's vaccinations until after next week's gatherings, according to Mina. And many kids ages 5 to 11 aren't vaccinated yet: Out of the 28 million who are now eligible, only about 900,000 had received their first dose by Nov. 10, according to White House data.

Other experts agree with Mina: It's a good idea to get kids one dose of vaccine before the holidays, Dr. Jill Weatherhead, an assistant professor of infectious diseases at Baylor College of Medicine, tells CNBC Make It.

"It may provide some protection, even having one dose," she says.

Vaccine-induced immunity isn't like flipping a light switch. Rather, your body mounts a little more protection each day in the weeks following your vaccination, eventually culminating in the specific, robust and strong antibodies that will target Covid, Weatherhead says.

"Even within a couple of weeks after the first dose, [kids are] likely to have some pretty good protection, at least for a short period of time," Dr. Kawsar Talaat, a vaccine expert at the Johns Hopkins Bloomberg School of Public Health, told the Washington Post earlier this month.

Mina also recommended having all attendees get rapid Covid tests the morning of any holiday get-together, which might be particularly good advice if anyone isn't fully vaccinated.

Beyond that, he wrote, you can reduce your party's risk of Covid transmission by hosting it outdoors or opening windows to improve ventilation, if weather permits. You could also buy a portable HEPA air filter, which can catch particles that contain SARS-CoV-2, the virus that causes Covid.

And if you're planning another get-together in December, you may have extra incentive to get your kids vaccinated soon: Anyone who gets their first dose by Nov. 19 will be fully vaccinated by Christmas Eve.

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