On Monday, a federal judge in Florida struck down the Biden administration’s mask mandate for airplanes, trains and other public transport. Within hours, several major airlines announced that they would no longer be enforcing mask requirements, and mask-wearing is optional. How can people continue to keep safe on planes now that masks are no longer required? What about vulnerable individuals like immunocompromised people and young children who aren’t yet vaccinated? Do you need to quarantine if you’re visiting vulnerable people and you were just on a flight? Should people consider canceling their travel plans? To help answer these questions, I spoke with CNN Medical Analyst Dr. Leana Wen, an emergency physician and professor of health policy and management at the George Washington University Milken Institute School of Public Health. She is also author of “Lifelines: A Doctor’s Journey in the Fight for Public Health.” The following conversation has been lightly edited for length and clarity. CNN: First of all, how worried are you about masks no longer being required on flights? Dr. Leana Wen: Since the beginning of the pandemic, I’ve said that my major concern with Covid-19 risk during travel isn’t what happens during transit, but what happens after people get to their destination. It may seem like planes are high risk because there are a lot of people in close proximity to one another, but planes have not been a major source of virus spread even before masking requirements. That’s because the ventilation on airplanes is quite good, with more frequent air exchanges than most office buildings. The HEPA filters they have are on par with the ones used in hospitals. That said, masks – especially when used properly and consistently – do reduce the risk of virus transmission. There could be higher risk now that masks are no longer required. That means people who wish to remain cautious must take matters into their own hands even more to protect themselves. CNN: What are steps people can take to continue keeping safe on planes? Wen: Just because masks aren’t required by the government doesn’t mean that you shouldn’t wear them. I have several trips this month by train and by plane, and I will certainly be choosing to mask in the airport, train station, on the train and plane, and in other crowded areas. If you are going to wear a mask, please wear a well-fitting, high-quality mask – an N95, KN95 or KF94 mask. I get very worried when I see people in simple cloth masks. They may think that those masks are protecting them, but they aren’t doing much, especially when we are dealing with the extremely contagious Omicron subvariants. Wear your mask in the highest-risk settings. That includes during boarding and deplaning, when the ventilation systems on airplanes are often not running. Don’t drink or eat at those times. Of course, please make sure you that you are maximally protected from a vaccination perspective. People who are vaccinated and boosted are less likely to be infected with Covid-19 compared with someone who is unvaccinated – and much less likely to become severely ill from the coronavirus. Consider getting your second booster shot, if you are eligible, for additional protection. CNN: What’s your advice for people who are immunocompromised, or families with young children not yet eligible to be vaccinated? Wen: For individuals who are immunocompromised or otherwise most vulnerable to severe outcomes from Covid-19, I would highly recommend that they stay masked with an N95 or equivalent mask at all times while in crowded indoor spaces. They should take off their mask to eat and drink only when not around others. That could be at an empty gate at the airport. One-way masking is highly protective, but only when it’s used at all times with a well-fitting, high-quality mask. For families with children, the question to ask is how important is avoiding Covid-19 to your family. If it is very important, what to do depends on the age of the child. Children ages 2 and older who are able to mask can be encouraged to mask while on flights. A cloth mask worn over a three-ply surgical mask is better than a cloth mask alone. It’s much more challenging for little kids and those who are unable to mask. My best advice is to put them in the window seat, turn on the air nozzle at full blast, and try to limit the time they have to be in packed, poorly ventilated spaces like during boarding and deplaning. CNN: What if you’re traveling to visit vulnerable people? Do you need to quarantine or test before seeing them if you just got off a plane with a lot of maskless people? Wen: Depending on the medical circumstances of the people you’re visiting, you may already be asked to quarantine and test. For instance, if you are visiting an elderly relative who is on chemotherapy, or meeting a newborn baby, their families may already be requesting that you limit your risks and not go to indoor dining for a few days prior to travel, then take a rapid test just before seeing them. I don’t think the travel itself should change this calculus. That is, I don’t think a plane of maskless people is risky enough to start your quarantine clock over, as long as you wore your N95 or equivalent the entire time while in indoor, crowded settings. CNN: The mask mandate decision doesn’t affect just airplanes and trains. It also impacts subways and buses, which a lot of people need to get to school and work, as well as medical appointments. Is it safe for them? Wen: This is a major concern. While airplanes have good air circulation in comparison to many other indoor settings, buses and subways may not. Also, many people need to take these local or regional forms of transportation in order to go about their daily lives. Some municipalities, such as New York and Los Angeles, are continuing to enforce mask mandates on local public transportation. My advice for vulnerable people remains the same: It is extremely important that you wear a well-fitting, high-quality mask at all times while in these indoor crowded spaces. Young children who are unable to mask and cannot yet be vaccinated have been at higher risk throughout the pandemic, and they remain at higher risk now. Try to limit their time in these settings and look for ways to improve ventilation, for example, by opening a window if that is an option. CNN: Are there some people who might want to reconsider travel plans, now that the mask mandate has essentially been lifted? Wen: I think families with babies and other very young children who are not able to mask might have already had concerns about traveling, especially with the number of people who were wearing flimsy masks or refusing to wear them. That’s the group that I could see being even more hesitant to go on planes and trains now. Other people who can wear an N95 or equivalent mask should be quite well-protected through one-way masking. I would urge vulnerable people – and really everyone – to have a plan for what happens if they were to contract Covid-19. Would they qualify for treatments? If so, which ones are best for them, given their medical circumstances and other medications they are on? How would they access treatment at their destination? Can they bring rapid tests with them, and if they need confirmatory PCR testing, where would they get it? Speaking of tests, before you go to international destinations, make sure you know what, if any, testing and vaccination requirements there are. There is still a testing requirement to reenter the United States, so know where you would go to get your test. In recent months, there has been a shift from top-down, federal mandates to empowering individuals to make risk calculations and then decide for themselves what precautions they want to take. For some people, it may not be ideal, especially considering the chaotic way the federal mask mandate was brought to an end, but we all need to adjust to the current circumstances. We have many more tools at our disposal, and people should know about how to access all these tools to protect themselves and their families.