Bolsonaro’s wife was vaccinated during their visit to New York for the U.N.G.A.

Jair Bolsonaro, Brazil’s proudly unvaccinated president, is contending with more fallout from his visit to New York last week to speak at the United Nations: A fourth member of his entourage has tested positive for Covid-19, and his wife, Michelle, opted to get vaccinated before they returned home.

Pedro Duarte Guimaraes, an economist who is the chief executive of Caixa Economica Federal, a leading Brazilian banking institution, disclosed on Sunday that he had tested positive, joining Brazil’s health minister, Marcelo Queiroga, Mr. Bolsonaro’s son Eduardo and a Brazilian diplomat. Mr. Queiroga, who was diagnosed during the visit, remained in isolation in a New York hotel.

Mr. Guimaraes and Mr. Queiroga have said they were fully vaccinated. Mr. Bolsonaro, whose insistence on downplaying the pandemic has been widely criticized, has declined to be vaccinated, contending that his own recovery from a Covid infection last year gave him resistance to a recurrence.

Defying a United Nations honor system requiring proof of vaccination, Mr. Bolsonaro was the first leader to address the General Assembly last Tuesday when it commenced the annual high-level week of speeches by representatives of its 193 members.

His delegation’s visit to New York also created an uproar from a widely circulated photograph showing him and subordinates eating pizza on the sidewalk. The host city of the United Nations requires proof of vaccination for indoor restaurant dining.

The potentially infectious Brazilians prompted United Nations officials to notify all diplomats at the organization who may have been in contact with them. As of Monday, none had reported testing positive, said Stéphane Dujarric, the U.N.’s chief spokesman.

Mrs. Bolsonaro’s vaccination, disclosed by Mr. Bolsonaro on Thursday after their return home, generated more adverse publicity, apparently revealing the couple’s lack of solidarity on that subject and — to some Brazilians — a disrespect by the Brazilian first lady for her country’s own health system.

“So what happened with my wife, just now in the United States. She came to me to ask: ‘Should I take the vaccine or not?’” he said during his weekly Facebook live chat. “I gave her my opinion. I’m not going to say what my opinion was. I’m going to say what she did. She took the vaccine.”

Mr. Bolsonaro, 66, also said: “She’s an adult, she’s 39, she knows what she’s doing and she got the vaccine.”

The president’s office sought to clarify the circumstances, explaining in a statement Friday night that all members of Mr. Bolsonaro’s entourage had to take a Covid test before boarding the plane back to Brazil. The statement said that during the test, the doctor administering it asked Mrs. Bolsonaro if she would like to be vaccinated.

“Since she had already been thinking about getting a shot, she decided to accept,” it said.

The statement did not identify the vaccine administered to her. Senator Omar Aziz, head of a parliamentary commission examining Mr. Bolsonaro’s handling of the pandemic, suggested she could have performed a patriotic duty by having been vaccinated at home.

“I congratulate Mrs. Michelle, who, unlike her husband, was vaccinated,” he told Brazilian media, but “someone should have told her that the vaccine applied in the United States is the same as in Brazil.” (In addition to the vaccines approved in the United States, Brazil has also used the Coronavac and AstraZeneca vaccines.)

Both Mr. and Mrs. Bolsonaro both tested negative on Sunday, his office said.

Nearly 600,000 Brazilians have died from Covid, the second-highest toll behind the United States, where more than 688,000 have died, according to a New York Times database, and only 41 percent of the Brazilian population has been fully vaccinated.

Ernesto Londoño contributed reporting.