Coronavirus Watch: Vaccinated and test positive? Here's what to know

Many Americans are wondering how to approach the holidays this year and safely travel and gather with friends and family, given the surge of the highly transmissible omicron variant.

What do you do if you have a close contact with someone with COVID-19? When do you become contagious? What do you do if you're vaccinated and test positive?

Health reporter Adrianna Rodriguez lays out CDC guidance and expert opinion here.

It's Tuesday, and this is Coronavirus Watch from the USA TODAY Network. Here's more news to know:

• President Joe Biden is expected to announce the purchase of a half-billion, at-home rapid tests and the mobilization of 1,000 military medical personnel to overburdened hospitals in an effort to confront surging infections and the omicron variant.
• A White House aide who was in close contact with Biden on Friday tested positive on Monday. Biden tested negative through an antigen test Sunday and a PCR test Monday, White House press secretary Jen Psaki. Biden will be tested again Wednesday.
• Massachusetts Gov. Charlie Baker announced he will activate up to 500 members of the National Guard to support understaffed hospitals and to bolster nonemergency medical transportation needs.
• U.S. population growth dipped to its lowest rate ever from July 2020 to July 2021, according to figures released by the Census Bureau.
• The director-general of the U.N. urged people everywhere to rethink holiday events. "It’s better to cancel now and celebrate later, (rather) than to celebrate now and grieve later,” Tedros Adhanom Ghebreyesus said.

Today's numbers: The U.S. has reported more than 51.1 million COVID-19 cases and 808,000 deaths, according to data from Johns Hopkins University. Worldwide, there have been more than 275.6 million cases and more than 5.3 million deaths. About 73% of people in the U.S. have received at least one vaccine shot, and about 61% are fully vaccinated, according to the CDC. Among U.S. adults, 85% have received at least one shot, and about 72% are fully vaccinated.

Tracking the pandemic: See the numbers in your area here. See where cases are rising here. See vaccination rates here. And here, compare vaccinations rates worldwide and see which countries are using which vaccines.

– Grace Hauck, USA TODAY breaking news reporter, @grace_hauck