Originally Published: 12 AUG 21 07:25 ET

Updated: 12 AUG 21 12:51 ET

By Katia Hetter, CNN

(CNN) -- As Covid-19 cases are surging across the United States again, daily infection rates are at their highest levels since February, due in large part to the very contagious Delta variant.

The US Centers for Disease Control and Prevention has once again urged a return to indoor mask-wearing, citing that even vaccinated people can get infected and pass Covid-19 to others.

Meanwhile, many people have travel plans for the rest of the summer and the upcoming Labor Day holiday weekend. Should they cancel their vacations? Is air travel safe? What if they are getting together with extended family or friends over the holiday -- what precautions need to be taken? And what about families with children too young to be vaccinated?

To help answer our many questions about travel and Covid-19 safety, we turned to CNN Medical Analyst Dr. Leana Wen. Wen is an emergency physician and visiting professor of health policy and management at the George Washington University Milken Institute School of Public Health. She's also author of a new book, "Lifelines: A Doctor's Journey in the Fight for Public Health," and the mother of two young children.

CNN: What should people consider when deciding whether to continue, change or cancel their travel plans?

Dr. Leana Wen: The most important factor to consider is the medical risk of your household. Specifically, is everyone in your house vaccinated? If everyone is vaccinated and generally healthy, you are very well-protected from getting severely ill from Covid-19. Many people in this circumstance might decide that they could take the risk of mild symptoms if they were to contract coronavirus and proceed with all their original travel plans.

If someone in your home is unvaccinated or immunocompromised, you may decide differently. A very low risk trip may still be fine -- for example, driving and then going camping and hiking with just your immediate family. But if the trip is going to involve spending a lot of time indoors with unmasked, unvaccinated people, I'd encourage the vulnerable individuals not to go on the trip. If some family members are still going to go, they could quarantine for at least three days upon return and then get tested before they get together indoors with vulnerable members of their household.

CNN: Would your advice depend on the location of the travel?

Wen: Yes, but in the US about 95% of the population lives in areas deemed by the CDC to have substantial or high levels of coronavirus transmission. I'd look at the specific area that you are thinking of traveling to and what you'd be doing there.

If you're driving to a national park, and the plan is to spend all your time hiking outdoors, that's very low risk. It doesn't really matter if the community around the park has high Covid-19 transmission, if you don't plan to interact with anyone there indoors.

That's very different from if you're planning a week of visiting museums, attending concerts, going to the theater and dining indoors. If those activities are taking place in a part of the country with a lot of virus transmission, you are being exposed constantly to Covid-19. The vaccines protect you well, but they are not 100%.

Risk is cumulative, and the more high-risk settings you are in, surrounded by people potentially carrying the virus, the more likely you are to experience a breakthrough infection even if you are vaccinated.

CNN: What's your advice for people who have booked international travel? Should they go?

Wen: It depends. Again, make sure to look at your own medical risk and the risk of those in your family. Consider the location you're going to. The CDC has updated information about Covid-19 by country divided into four levels of risk.

In addition, the US State Department has helpful information including the protocols that you need to follow in order to enter the country. Make sure to know the requirements. Some countries require proof of recent negative tests, for example, and some are beginning to require vaccination. Keep in mind that rules are constantly changing and stay flexible.

CNN: What about getting together for a wedding -- would that be safe?

Wen: Once again, it depends. Many weddings involve people converging from different parts of the country or the world. That adds risk, especially since there are so many places with high levels of Covid-19 infection. It would certainly help if the hosts required that everyone attending is vaccinated.

Vaccinated people have an eight-fold reduced chance of contracting Covid-19 compared to unvaccinated people, according to estimates based on CDC data. If the ceremony and reception are both held outdoors, that would also reduce the risk. The opposite, of course, would be true of indoor gatherings of people of unknown vaccination status, who are eating and drinking and therefore not wearing masks. That would be a high-risk event.

CNN: Can we talk about modes of transportation -- specifically plane travel. Is that still safe for vaccinated people? What about unvaccinated children?

Wen: Plane travel is still relatively safe for vaccinated people. Make sure to wear a high-quality mask at all times -- ideally an N95 or KN95 mask. If you have to eat and drink, do so quickly, so as to minimize the amount of time you're not wearing a mask.

Children too young to be vaccinated should also mask, if possible, with at least a 3-ply surgical mask. If they cannot keep on the mask for the duration of the trip, I would consider not bringing the child unless it's an essential trip, such as moving across the country.

In my family, my husband and I will travel by plane and wear N95 or KN95 masks the entire time. Our son, who is almost four, is generally good about wearing masks, and if we had a short trip of a few hours' flight, he'd be fine. But we have a 16-month-old daughter who is too young to mask. We would not feel comfortable bringing her on a flight right now.

Other families may make different decisions based on their level of risk tolerance as well as the value of the travel to them. For where we are in the pandemic, the risk is not worth the benefit to us.

CNN: Driving, going to rest stops, staying in a hotel en route -- that's all pretty safe from a Covid-19 standpoint, right?

Wen: Yes. Of course, use common sense -- wear masks when going to the restroom in rest stops. Order carryout instead of eating indoors. Go directly to your room in the hotel, and don't hang out in crowded hotel lobbies and bars.

CNN: What's your advice for families who want to rent a house together?

Wen: The safest scenario is if everyone is fully vaccinated. If there are people who are unvaccinated, or if the people gathering want to reduce their risk further, everyone who wants to get together can essentially quarantine for three to five days and then get tested. By quarantine, I mean to reduce your risk by not getting together with other people indoors and not participating in higher-risk activities like indoor dining.

I know that this advice feels like we have taken a step backwards. It's true -- we have. Covid-19 cases are on the rise again, and we have the more contagious Delta variant to contend with.

Vaccination is the single most important step to protect us. In addition, depending on our individual circumstances, we should consider additional precautions to reduce risk and keep our families safe, while still enjoying travel.