Dear Tripped Up: I’ve had my first vaccination shot and plan to book a flight to California two weeks after my second one. Like so many others, I have not seen my grandchildren for more than 15 months. Now that some of us are getting successfully vaccinated and are planning on flying to see our families, I have a few questions. — Margot

Is it safe to travel by subway, train, bus or plane after I have been vaccinated? What are the proper protocols for protecting others?

Even before the vaccines arrived, mass transit was rarely labeled by health officials with blanket terms like “safe” or “unsafe.” Studies conducted over the summer suggested that when certain criteria are met, subways are safer, from a viral-transmission standpoint, than one might assume. A trove of new research indicates that the chance of contracting the coronavirus while flying is low. For trains and planes alike, the focus is — and will continue to be — concrete, actionable measures that mitigate risk, like high-efficiency air filtration, enhanced disinfection, mask requirements, social distancing and capacity limits.

With that in mind, let’s rephrase your first question:

“It is safer for her, as the individual, to travel that way, and not herself get sick,” said Keri N. Althoff, an associate professor of epidemiology at the Johns Hopkins Bloomberg School of Public Health, deliberately emphasizing those italicized words.

“We know that vaccines protect the person who has been vaccinated from getting really, really sick to the point of hospitalization or death,” Althoff said. “But we don’t know whether or not a vaccinated person can still become infected and transmit either asymptomatic infection or very mild unnoticed infection. We’re still waiting for the data.”

Only about 8% of the United States population has gotten at least one shot, according to the latest numbers, which means you’re in the minority now.

That’s why the second part of your question is so important, and why the basic protocols for protecting others (masks, distancing, hand-washing) ­haven’t changed. It’s also why airlines and other transportation companies are nowhere close to getting rid of them. In fact, those protocols have been strengthened in recent weeks by the Centers for Disease Control and Prevention, which has issued a mask mandate for all domestic transportation.

“I know it’s frustrating, especially for grandparents, because it almost feels like the goal posts have been moved again,” Althoff said. “But we’ve always said that you cannot just rip your mask off and run around like it’s 2019 once you’re vaccinated. We’ve all learned not only how important our individual health is, but also how interconnected we are.”

Do I need a negative virus test to fly if I have a vaccination card?

For the time being, vaccination cards don’t supersede — well, much of anything.

Last week, the CDC enacted an order requiring a negative coronavirus test for all incoming international travelers (ages 2 and older), including United States citizens. The test must be completed within three days of departure and submitted to the airline before boarding, and there are no exceptions for antibody or vaccination status.

“It’s directly related to the fact that we don’t know if people who are vaccinated are also protected from infection and cannot transmit,” Althoff said. “So those guidelines are going to stay in place until the science says differently.”

Do I need to follow each specific state’s quarantine regulations if I have been fully vaccinated? Such a requirement would make it very difficult to travel.

With the exception of New Hampshire, which now allows people who are 14 days past their second shot to skip quarantine, most states are still requiring fully vaccinated people to adhere to quarantine requirements.

“States are being conservative and waiting for that data,” Althoff said. “That’s why the CDC and most public health leaders are not recommending any travel until things calm down. Vaccine or not, there are no silver bullets here.”

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