The U.S. Centers for Disease Control and Prevention (CDC) has made some changes to its guidance for people visiting the United States from other countries.

On Thursday, the national public health agency posted an update to its requirement for proof of COVID-19 vaccination for air passengers on its website.

According to the new guidance, international travelers coming to the U.S. are considered fully vaccinated if they received a single-dose vaccine two weeks before their flight. The same can be said for those who had their second dose of a 2-dose series 14 days prior.

With the new guidelines, anyone who got a single dose of either the Pfizer or Moderna MRNA vaccine after Aug. 16, 2022 - the time when the bivalent vaccines became available - is considered fully vaccinated. Thus, they are allowed to travel provided they had it at least two weeks before their flight.

The updated guidance aligns with the CDC's simplified vaccination program for Americans, which considers previously unvaccinated people fully vaccinated once they received a single dose of the bivalent formulation, designed to protect against the original strains and the more recent variants, per CNN.

Those who received the monovalent formulations can only qualify as fully vaccinated foreign visitors when they have completed the series. This means recipients of the two-dose Pfizer, Moderna, Novavax, AstraZeneca, Covaxin, Covidshield, BIBP or Sinopharm, CoronaVac, Nuvaxvoid, Covovax and Medicago would only be allowed to fly to the U.S. if they have completed the series.

Meanwhile, recipients of the single-dose Johnson & Johnson's Janssen vaccine and the Chinese-made Convidecia are considered fully vaccinated.

It is important to note that the travel requirements do not apply to U.S. citizens, lawful permanent residents (Green Card holders), or immigrants. They only apply to international
travelers planning to visit the country.

"If you are not fully vaccinated against COVID-19, you will NOT be allowed to board a flight to the United States, unless you meet the criteria for an exception under the Proclamation and CDC's Amended Order," the CDC stated on its website.

Exceptions only apply to persons on diplomatic or official government travel, children under 18 years old, persons with documented medical contraindications to the COVID-19 vaccines, participants in vaccine trials and persons issued a humanitarian or emergency exception, among others.