“The airlines will verify vaccination status in same way they have been, and will continue to do, with pre-departure negative Covid test results,” a senior Biden administration official told reporters Monday.

Those under the age of 18 will be exempted from these requirements, in large part due to the limited availability or authorization of Covid-19 vaccines for children across much of the world. Children aged 2 or older will be required to have a negative Covid test prior to their flight.

The U.S. first outlined the impending international travel rules for fully vaccinated individuals in mid September.

“We have taken the deliberate step of taking this time to ensure implementation goes as smooth as possible, particularly with something this wide ranging,” a second senior administration official told reporters on Monday.

The rules also include an exemption for people hailing from a country with limited vaccine availability, which the Biden administration is defining as a place where less than 10 percent of the population is fully vaccinated “due to lack of vaccines,” according to one senior administration official. There are roughly 50 countries that fall under that threshold, including much of Africa.

However, that official added that unvaccinated individuals who qualify will have to demonstrate a “specific, compelling” reason for traveling to the U.S. and test negative one day prior to their flight. Any child traveling with an unvaccinated adult will also have to show proof of a negative test within that same window.

Unvaccinated U.S. citizens or lawful permanent residents will also have to show proof of a negative test one day prior to boarding, down from three days. Fully vaccinated individuals will continue to have three days to get tested.

There are a handful of other narrow exceptions to the vaccination requirement, such as for foreign nationals who had severe allergic reactions to a prior Covid-19 vaccine dose.

U.S-bound travelers will also have to submit information to airlines, such as working phone numbers and email addresses, to allow health officials to conduct contact tracing if travelers have been potentially exposed to the coronavirus.

The announcement of the new rules comes days before President Joe Biden's planned trip to Europe for a set of summit meetings with other global leaders, as well as Pope Francis.

The U.S. is also scheduled to reopen land and ferry crossings to fully vaccinated travelers the same day as the air travel rules, Nov. 8. The borders have been closed to non-essential, discretionary travel since March 2020 and in recent months had become a major source of frustration within the Canadian government and among U.S. elected officials representing communities along the northern border.