The American Airlines Center in Dallas announced Tuesday afternoon that a pair of Elton John concerts at the venue have been postponed because the singer recently tested positive for the coronavirus.The announcement came just hours before the planned start of a show, which was to begin at 8 p.m. on Tuesday. The second concert had been scheduled for Wednesday.In a brief statement on its website, the American Airlines Center said, “Elton is fully vaccinated and boosted, and is experiencing only mild symptoms.”The shows are part of his “Farewell Yellow Brick Road” tour. The American Airlines Center did not give new dates for the concerts.

It is the first major performing arts institution to require boosters, as concern mounts over rising coronavirus cases and the spread of the Omicron variant. The rule will take effect Jan. 17.The Metropolitan Opera announced Wednesday that it would require all eligible adult employees and audience members to get Covid booster shots in order to enter the opera house, making its safety measures stricter than those on Broadway or at other venues.The Met is the first major performing arts organization in the city to announce a booster-shot mandate that will apply to audiences as well as staff members; the new rule will take effect Jan. 17. The policy was announced as concern about rising caseloads and the spread of the Omicron variant is mounting: The average daily number of coronavirus cases in the city has more than doubled over the past two weeks.“We think we should be setting an example,” Peter Gelb, the general manager of the Met, said in an interview. “Hopefully we will have an influence on other performing arts companies as well. I think it’s just a matter of time — everyone is going to be doing this.”It is not the first time that performing arts organizations, eager to reassure audiences that they could safely visit theaters, have imposed virus prevention measures that went beyond government mandates. When Broadway theaters announced over the summer that they would require audiences to be vaccinated and masked, it was several days before Mayor Bill de Blasio announced that New York City would impose a vaccine mandate for a variety of indoor spaces, including performing arts venues.Since the Met reopened after losing more than a full season to the pandemic, it has required that staff members and patrons be fully vaccinated to enter the opera house. But Gelb said that it had become “obvious” to him that even stronger safeguards were now necessary.“It’s of paramount importance that the audience members and employees feel safe when they enter the building,” he said. “To me, there is no question — this is the right move.”Since November, the Centers for Disease Control and Prevention has recommended booster shots — either six months after people receive a second Pfizer or Moderna shot, or two months after a single dose of the Johnson & Johnson vaccine.When the Met’s new rules take effect Jan. 17, people eligible for booster shots will be required to have them to enter the opera house. (There will be a short grace period: People will be allowed in unboosted if the performance falls within two weeks of the date they become eligible for boosters. People who are not yet eligible for their booster shots will still be allowed in.) Inside the opera house, people will be required to wear face masks, except when they are eating or drinking in the limited areas where that is allowed.Met officials said that they reviewed their new policy with leaders of the various unions that represent its workers in advance of Wednesday’s announcement and described the union response to the rules as “very positive.”Len Egert, the national executive director of the American Guild of Musical Artists, said that union officials had determined that at the Met, “boosters are warranted,” and had subsequently bargained to make sure its members’ rights were protected.Adam Krauthamer, the president of Local 802 of the American Federation of Musicians, said his union “applauds the Met’s plan to make vaccine boosters mandatory” and called the move “a necessary step forward to ensure the public’s safety and keep N.Y.C. as a beacon of live performance.”The company has adopted strict safety measures since reopening; in October, choristers wore masks backstage during a performance of “Die Meistersinger von Nürnberg.” Todd Heisler/The New York TimesIt was not immediately clear whether other arts institutions would follow the Met in tightening their Covid rules. Gelb said he had informed the leaders of Carnegie Hall, the New York Philharmonic and Lincoln Center that the Met would soon be adding a booster-shot mandate.The announcement that the Met would enact stricter Covid protocols came a day after a performance of the ballet “Don Quixote” was canceled at the Opéra Bastille in Paris because officials said someone in the company tested positive for the virus. Several Broadway shows have recently had to cancel performances because of positive Covid tests among the cast and crew. And in the National Football League, 37 players tested positive Monday, the highest single-day total since the start of the pandemic.The Coronavirus Pandemic: Key Things to KnowCard 1 of 4Pfizer’s Covid pill.