With a growing number of states rolling out vaccines to the general public, most US adults could get their hands on a shot by summer, if not sooner. So far, 29 percent of the US population has received a first dose.

But until a majority of the country has been vaccinated, it's tough even for vaccinated people to determine what's safe. Although the Centers for Disease Control and Prevention offers basic guidelines for vaccinated Americans, quite a few common scenarios aren't addressed in the agency's recommendations.

For instance, the CDC doesn't offer advice for households in which only some family members are vaccinated, or for people who've received just one vaccine dose.

The guidance also stops short of telling vaccinated people whether they can return to indoor activities, and there's no concrete rule about exactly how many fully vaccinated people can gather indoors without masks.

So we asked physicians to weigh in on a handful of these common yet confusing scenarios. In general, they said, vaccinated people can incur more risk if they live alone or with others who've gotten their shots.

Wait to get both shots before changing your behavior
The CDC doesn't consider a person to be fully vaccinated until at least two weeks after their second dose of Pfizer's or Moderna's vaccine, or two weeks after their single shot of Johnson & Johnson's. That's because it takes time for immunity to build.

Dr. Vivek Cherian, an internal-medicine physician in Baltimore, told Insider that it's not worth the risk to start changing your behavior in between your first and second shot.

"You'd be really only talking about waiting an extra few weeks to get your second dose and reap those benefits," he said.

Steer clear of large gatherings if you live with unvaccinated people
The CDC says it's alright for vaccinated people to remove their masks when visiting other fully vaccinated people indoors or seeing unvaccinated people from a single household.

"The guidance is fairly straightforward," Dr. Jonathan Leizman, a family medicine physician and the chief medical officer at Premise Health, told Insider. "What is not always straightforward, though, are real-life circumstances. Split households, where some members are vaccinated and others are not, is one example."

Physicians generally advise that these households stick to outdoor activities and steer clear of large gatherings until all members have gotten their shots.

For example, Cherian said, in his family, he's vaccinated but his wife and children aren't. So they've chosen to refrain from activities with crowds – such as birthday parties – even if they're outdoors. 

"Given that our older son is attending a school that is practicing safety against COVID-19 by maintaining learning pods, we feel an even greater ethical responsibility to reduce risk as much as possible," he said. 

Households with high-risk individuals should be extra cautious
Leizman said it's important to consider whether unvaccinated people in your household are vulnerable to severe COVID-19. If that's the case, even the vaccinated person should continue to wear masks in public and ensure any gatherings with people outside the home are socially distanced and outdoors. 

"In instances where one member of a couple is unvaccinated and does not have risk factors for severe COVID-19, [the couple] may socialize indoors and without a mask with another adult who is fully vaccinated," Leizman said. 

Big groups of fully vaccinated people aren't necessarily risky
The CDC recommends that vaccinated people continue to avoid medium and large in-person gatherings – but the agency doesn't give a specific cutoff for the number of attendees. Experts don't yet seem to agree about whether multiple households of fully vaccinated people should gather in groups. 

"The time for concerts, weddings, and other large-scale events will certainly come, and the risk of creating a superspreader event is certainly lower if participants are vaccinated," Leizman said. But he added that "vaccination is truly only one part of the public health puzzle."

For now, he suggested that "fully vaccinated people should avoid these types of gatherings."

But Cherian said the size of the event isn't the main issue – it's whether any unvaccinated people are in attendance.

"If all individuals are fully vaccinated, there is an extremely low risk to those present," he said. "When you start having larger gatherings and include unvaccinated individuals from many different households, the risk of COVID-19 transmission increases."

There's little harm in hopping on a plane if you're vaccinated
The CDC recommends that fully vaccinated people continue to refrain from non-essential travel, but the guidelines don't specify which forms of travel are off-limits.

Experts said there's little risk in hopping on a plane to see friends and family once you're fully vaccinated. 

"Fully vaccinated people should feel free to travel to see their families," Dr. Leana Wen, an emergency physician in Baltimore, told CNN. "But of course, please take every precaution during the travel – including wearing a well-fitting mask at all times in public places, trying to stay physically distanced where possible, and washing hands well."

It's ok to take the subway, but wear your mask
Subways, trains, and buses tend to hold large crowds, so riders face a higher risk of COVID-19 exposure. For that reason, the CDC still recommends that Americans limit their use of public transportation if possible, whether they're vaccinated or not.

Leizman, however, said that vaccinated people can consider taking the subway if they wear masks and practice social distancing whenever possible.

Be selective about high-risk activities like indoor dining or church services
Wen told CNN that she considers the CDC guidelines for vaccinated people to be "overly cautious" about indoor activities.

"Let's say that someone is vaccinated and really wants to attend in-person church services and to go back to their senior center for indoor activities," she said. "The risk to them is very low, and their risk to others is also low."

The same goes for indoor dining, Wen added: "I'd go so far as to say that a couple that really wants to eat out in a restaurant again could do so occasionally, but not night after night."

In general, experts recommended that vaccinated people choose the indoor activities that matter most to them, then engage in these activities sparingly until most others are vaccinated as well.

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