Federal health authorities on Monday warned against travel to 15 countries and territories, including Costa Rica, the United Arab Emirates and five Caribbean destinations, because of "very high" risk levels of coronavirus.
By issuing Level 4 advisories, the Centers for Disease Control and Prevention said that "even fully vaccinated travelers may be at risk for getting and spreading COVID-19 variants" in those locales. The new additions expand a list of more than 100 destinations to receive the agency's highest travel warning.
In the Caribbean, the CDC urged people to "avoid travel" to Jamaica, Saint Barthelemy, the Dominican Republic and two island territories of France: Guadeloupe and Saint Martin. The agency also issued its highest coronavirus warning for Peru, Colombia, Fiji, Kuwait, Mongolia, Niger, Romania and Tunisia.
Monday's alerts deal with some of the most popular beach destinations for Americans. According to federal travel data, more than 4.6 million U.S. citizens traveled to the Caribbean from January through September last year. That exceeds the number of U.S. visitors to any other overseas region, including all of Europe.
Other Caribbean tourist spots designated as highest-risk include the Bahamas, Barbados and Sint Maarten, which is part of the Netherlands and on the same island as Saint Martin.
Video: Is it safe to travel as omicron spreads?
The CDC's latest advisories come as some countries ease travel restrictions and project optimism that cases of the highly transmissible omicron variant have peaked within their borders. British officials said Monday that starting Feb. 11, fully vaccinated travelers will no longer have to take a coronavirus test within two days of entering England. Thailand plans to significantly shorten quarantine periods for visitors who are fully vaccinated based on their test results.
But the explosion of cases driven by omicron continues to weigh on travel plans, and the CDC has issued a steady stream of warnings.
The CDC is not advising against all travel to Mexico, which saw the most U.S. tourism in the first nine months of 2021, with nearly 20 million American visitors. But it says unvaccinated people "should avoid nonessential travel" there.
The CDC uses a four-level system of coronavirus travel warnings. Destinations are generally moved to the highest tier if they sustain infection levels of more than 500 new cases per 100,000 people over 28 days, though authorities also take testing and the trajectory of new cases into account as well.
The CDC said if people must travel to the destinations that were just marked Level 4, they should get fully vaccinated against the coronavirus first. The agency urges against international trips for those who are not vaccinated, but it says people should get tested one to three days before leaving if they do travel.
Health officials have emphasized that some vaccinated people will contract the virus, particularly as omicron proves more resistant to existing vaccinations. Research shows that omicron tends to cause less severe illness than the delta variant, which became dominant last year.
Vaccinations appear to protect against the most serious infections, experts say, especially for those who have gotten a booster shot.