Lack of comprehensive evidence on Covid-19 transmission is prompting the CDC to be overly cautious on its guidance to vaccinated people who want to travel, epidemiologists and doctors say.
The Centers for Disease Control and Prevention didn’t include any changes to travel guidance for fully vaccinated individuals in its recommendations released Monday. The CDC continues to urge that people delay travel.
The main concern for vaccinated people traveling would be spreading Covid-19 to other travelers. The three vaccines authorized by the Food and Drug Administration are highly effective at preventing infection and serious illness in vaccinated people, but evidence is still early on whether those individuals can transmit the virus.
CDC Director Rochelle Walensky pointed to concerns about spread of new variants of the virus when asked why the CDC declined to update the guidance.
“Every time that there is a surge in travel we have a surge of cases in this country,” Walensky told reporters Monday. “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.”
The CDC hopes that by the next update it will have more scientific guidelines as to what vaccinated people can do, “perhaps travel being among them,” Walensky said. She didn’t specify when the next update might be.
Not Getting Ahead of the Science
Walensky “will make progress on guidance, she’ll evolve guidance to change it, but I don’t think she’ll get ahead of the science,” said Sten Vermund, professor of public health at the Yale School of Public Health. “I’m willing to get ahead of the science based on highly plausible and probable circumstance, and she doesn’t have that luxury as the head of the CDC.”
“We don’t know how well vaccinated people can be spreaders. There’s a lot of research going on now,” said David Freedman, professor emeritus of infectious diseases at the University of Alabama at Birmingham. “We think we’re going to find the vaccinated people do not spread very efficiently, but we just have no way of knowing that now.”
Seven studies have shown that the risk of transmitting the virus after being fully vaccinated is very low. However, some scientists say that isn’t enough to change the travel guidance. That evidence was likely what led the CDC to also update its recommendations to say that vaccinated people don’t have to quarantine unless they are symptomatic.
“Scientifically, it doesn’t make sense” to not require quarantine and also not recommend travel for people who are vaccinated, said Monica Gandhi, professor of medicine and associate division chief of the Division of HIV, Infectious Diseases, and Global Medicine at the University of California, San Francisco and Zuckerberg San Francisco General Hospital.
Not updating the travel guidance is an “oversight,” Gandhi said. “I don’t see any point why vaccinated people can’t travel.”
“People are so nervous, including the CDC themselves, of loosening restrictions,” she said.
Vermund and Freedman, who are vaccinated, each said they have plans to travel in the coming months
However, other scientists think the CDC is taking the correct, cautious approach.
“We are not anywhere near having a large enough percentage of our population vaccinated, to really start to loosen these guidelines now,” said Amira Roess, professor of global health and epidemiology at George Mason University. “I tend to think that that might be partly why we saw very minor changes made.”
About 10% of people in the U.S. are fully vaccinated as of Tuesday, according to Bloomberg data.
If I was the CDC, “I would like to have some confidence on the evidence base on which I’m making my judgment, and until that time I might choose a more cautious advisory,” Vermund said.
The CDC may have felt it was “premature” to update the travel guidance, said Wafaa El-Sadr, professor of epidemiology and medicine at Columbia University, and it “behooves all of us” to wait until more people are vaccinated to do so.
“There is reason to really try to slow down our movement. When humans move from place to place, we move with us microbes,” and with Covid-19 “we have reason to be concerned about the emerging more transmissible variants that are popping up in multiple places, and we really would like to try to limit the spread,” said Roess.
Updates to Come
Travel guidance “will get better when we get more evidence that the transmission risks for travelers is low for fully vaccinated people in large settings like those seen when we travel,” said Georges Benjamin, executive director of the American Public Health Association.
Vermund said, “In the next few weeks we may very well have more convincing data, and that will be the kind of data that one can then change policy.”
—With assistance from Jeannie Baumann