The United States hit an important milestone in its fight against the coronavirus pandemic this week: Over 9 percent of Americans are fully vaccinated against the disease, White House officials said, a number that exceeds the country’s total number of confirmed coronavirus cases. Such a benchmark shows we’re “turning a corner,” the Biden administration said — but not yet for travel.

The White House’s announcement coincided with Monday’s issuance of guidance for fully vaccinated Americans by the Centers for Disease Control and Prevention. Under that guidance, vaccinated people two weeks from their second and final shot can safely hold small indoor gatherings with other vaccinated people, without masks or distancing. They may also reasonably visit with low-risk unvaccinated individuals, such as children, without masks. Travel, however, still is deemed inadvisable because of the potential for vaccinated people to carry and transmit coronavirus to others who are not vaccinated.

“At this time, the CDC is not adjusting current guidance on travel,” Andy Slavitt, White House senior adviser on the covid-19 response, said in a press briefing announcing the guidance. The country, he said, remains “in the midst of a serious pandemic, and still over 90 percent of our population is not fully vaccinated, though we are working hard to get there.”

Yet officials in the health and travel industries disagree as to whether such caution is warranted at this point in the pandemic, as vaccinations in many countries ramp up but coronavirus variants continue to stir global concern. Besides forgoing nonessential travel, the CDC guidance says both vaccinated and unvaccinated Americans should continue to avoid medium- and large-sized gatherings and wear face masks and physically distance in public spaces.

Leana Wen, an emergency physician and public health professor at George Washington University, pushed back against the CDC in an appearance Monday on CNN, saying that the agency “is being far overly cautious in a way that defies common sense.”

Wen pointed to evidence that vaccinated people are less likely to transmit the coronavirus, as well as new CDC quarantine guidance that says vaccinated travelers do not need to quarantine after exposure to covid-19 if they do not display symptoms.

“It just doesn’t make sense that you can’t travel, especially if you now can get together with loved ones. I think people are eager to see their grandkids, who they don’t necessarily live with, and so I think it’s really important to give the guidance about travel,” Wen said. “And I actually would go further and say that people who are fully vaccinated should be able to travel, should be encouraged to travel, and that’s one of those incentives we can give” for people to become vaccinated.

Airlines for America, a trade group composed of the largest air carriers in the United States, swiftly spoke out against the guidance as well. The organization said in a statement that it considers planes to be low-risk environments for covid-19 and that mandated mask-wearing as well as high-efficiency air filtration on planes represent a “layered approach [that] significantly reduces risk” of transmission.

But other health experts and U.S. health officials say overt caution now is the point, and it could facilitate a quicker return to travel later. Carlos Acuna-Villaorduna, an epidemiologist at Boston Medical Center, says the more-contagious covid-19 variants that have entered the United States, particularly those first identified South Africa and Brazil, require extreme caution to prevent another wave of cases.

“The rationale of the CDC is to not be overtly optimistic, because of the possibility of travel exposing people to these covid variants,” Acuna-Villaorduna said. “We don’t know yet what are going to be the true effects of these variants, and it might be a minor effect, but the worst-case scenario here is that if a tricky variant, particularly the South African one, [takes over], we are going to have a third wave, maybe even a fourth wave, in this country.”

While data suggests vaccinated people will circulate less of the virus, he noted, the variants’ transmissibility makes even a small number of cases riskier.

CDC Director Rochelle Walensky said Monday that pandemic trends support a need to discourage Americans from traveling.

“Every time that there’s a surge in travel, we have a surge in cases in this country,” Walensky said. “We know that many of our variants have emerged from international places, and we know that the travel corridor is a place where people are mixing a lot. … Our next set of guidance will have more science around what vaccinated people can do, perhaps travel being among them.”

U.S. airlines asked the White House this week for standardized requirements for covid-19 documentation, the Associated Press reported. In a letter to President Biden, industry leaders pressed for uniform standards for vaccine passports and internationally recognized testing certificates that would facilitate a return to travel.

Despite CDC recommendations, it’s clear that Americans are still traveling. Transportation Security Administration data monitoring the number of daily screenings has consistently surged around holiday periods, hitting more than 1 million travelers per day, in increasing frequency, over the December holiday period and over long weekends such as Presidents’ Day in February.

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