At John F. Kennedy International Airport in New York on Sunday night, the pickup area at Terminal 1 was filled with people who had arrived on the last flight from Moscow before the new rules took effect. Russia was not one of the 33 countries under the old ban, but the Russian-made Sputnik V vaccine is not on the list of coronavirus vaccines that are now being accepted for entry to the United States. So the door to the United States shut for many Russians at one minute after midnight Eastern time on Monday.

A woman traveling from Russia with two young children acknowledged that the vaccine rules had affected the timing of their trip, before declining to be interviewed.

Another arriving traveler, Vyacheslav Alexov, waited for a car to collect him and his carefully plastic-wrapped luggage. He had cut short a trip to see relatives in Kazakhstan in order to make sure he was back in the United States before the new rules took effect on Monday.

As a permanent U.S. resident, he is allowed to travel in and out of the country just as American citizens can, by showing a current negative coronavirus test. But Mr. Alexov, who said he was not vaccinated, was worried that he might be blocked anyway.

“It’s political,” he said of the new policy to require foreign travelers to show proof of vaccination, but not accept the Russian vaccine.

Travelers from Colombia had not faced restrictions before Monday, but now they too must be fully vaccinated. Juan David Peláez, 43, who owns an insurance company in Bogotá, has been planning a family trip to the United States since February. Mr. Peláez, his wife and son, his parents, and his brother and sister-in-law had been set to arrive on Monday.

But Mr. Peláez said that though he is vaccinated with Moderna, he has not yet received an official vaccine certificate from the government and worried about being able to provide proof. He switched his own ticket, as well as that of his wife, who is also vaccinated, and that of his young son, to arrive on Nov. 7, a day before the rest of the group.

The changed rules “affect a lot of people who would not have been affected in the past,” said Mr. Peláez, while waiting for his family in an arrivals hall at Miami International Airport on Monday. “I would have missed out on the trip.”