Unvaccinated children and some people from countries with low rates will be exempted from new U.S. travel rules.

Children under the age of 18 who are unvaccinated against the coronavirus, and a limited category of foreigners arriving from countries with low vaccination rates, are among the travelers exempted from forthcoming requirements that will determine who can enter the United States, Biden administration officials said on Monday.

The Biden administration has announced that it would lift travel restrictions on Nov. 8 and reopen the United States to fully vaccinated international travelers who had been barred for nearly a year and a half from entering the country by air or crossing the land borders.

But the new travel system also comes with stringent requirements, and will seal the United States off from most foreigners who have not yet received a vaccine cleared by the World Health Organization or U.S. federal regulators. On Monday, senior officials detailed opportunities to enter the United States for certain travelers who struggled to obtain a vaccine because of a lack of uniform vaccine eligibility for minors, as well as limited access to the global supply.

Unvaccinated children under the age of 18 will be permitted to enter the United States when the new system takes effect, officials said, confirming an earlier report from The New York Times. Children older than 2 who are traveling with a fully vaccinated adult will need to show a negative coronavirus test within three days of their departure date. Those traveling alone or with an unvaccinated adult will need to show such a result one day before they travel to the United States.

The exemptions will also apply to adults flying from countries where less than 10 percent of the overall population is fully vaccinated, if they can show a “compelling reason” for entering the United States, officials said. That carve-out, they said, would apply to a narrow group of unvaccinated travelers; entering the United States for tourism would not clear the bar for an exemption.

Others who show a U.S. government-issued letter approving an emergency or humanitarian need to travel will also be allowed to cross U.S. borders.

Many leaders in the tourism industry have praised the new rules, which will signal a new chapter in the U.S. recovery from the pandemic. The restrictions imposed in the early days of the pandemic have barred tourists and separated family members from traveling to the United States for nearly 18 months.

But on Nov. 8, the country will open to those who can show that two weeks have passed since they received either a second shot of the two-dose vaccines cleared by U.S. federal regulators or the W.H.O. (in any combination), or a single shot of a one-dose vaccine greenlit by those organizations, like the one from Johnson & Johnson. Digital or print proof of vaccination status will be required.

In addition, fully vaccinated American citizens or legal permanent residents arriving by sea or air will need to show proof of a negative coronavirus test taken within three days of traveling. Those who are unvaccinated will need to test negative within one day of traveling. Those crossing the land border from Canada or Mexico will not have a testing requirement.

Travelers will also be required to provide their personal information for potential contact tracing after arriving in the United States.