Understudies became the season’s heroes: One night at “Come From Away,” nine of the 12 performers were standbys, including alumni and members of touring companies flown in to help out. At “Thoughts of a Colored Man,” the playwright performed to save a night; at “Macbeth,” the director did the same. Last week, at “Girl From the North Country,” the actor Anthony Edwards, best known for “ER,” stepped onstage with a script after just an hour of rehearsal, eager to help a show that stars his Tony-nominated wife, Mare Winningham.

That resourcefulness has curtailed show cancellations, but hasn’t eliminated them. Last weekend, “Moulin Rouge!,” which last year won the Tony Award for best musical, canceled four performances, while “The Skin of Our Teeth” canceled three.

And coping with Covid has been costly. For instance, one midsize production, the Tony-nominated revival of “Caroline, or Change,” spent an additional $10,000 to $15,000 each week on pandemic precautions, according to Sydney Beers, the executive producer at Roundabout Theater Company, which presented the show.

Roundabout increased its spending on immigration lawyers — the show’s Tony-nominated star, Sharon D Clarke, and six members of its creative team are British, and when rehearsals resumed, travel was still restricted. The theater hired extra understudies, knowing Covid might lead to more absences. And it built a three-person Covid safety team that ran 7,000 PCR tests during the show’s three months, testing every employee at least three times a week, and sometimes daily, depending on city caseloads.