Dismissal last fall at P.S. 295 in Park Slope, Brooklyn.Credit...Benjamin Norman for The New York Times

“I have always said that the science will guide us out of the pandemic, and because we have followed the data, which shows that cases are steadily falling, we’ve beaten back the latest Covid-19 surge,” said Mayor Adams in a statement.

The city is still strongly recommending that masks be worn indoors for people of all ages, however, as new, confirmed cases still remain at a high level despite recent declines. The city’s alert level is also still orange, or high, but Mayor Adams has repeatedly said he will remove or implement mandates as he and his advisers see fit, rather than wait for his alert system to trigger actions.

The toddler mask mandate has been a subject of great contention in New York City as one of the last mandates the mayor has left in place during the pandemic. The mayor lifted mask mandates for older school children, along with vaccination verification policies at bars, restaurants and indoor entertainment venues, in early March. He also declined to reinstate a wider indoor mask requirement when the city went to a high alert level in mid-May, even though his alert system recommended it.

While some toddler parents supported the mandate, a loud contingent of parents have confronted the mayor on the issue, saying that their children’s intellectual and emotional growth was being stunted because of masks. The mayor had promised repeatedly to remove the mandate when he felt the time was right.

With school set to end in New York City on June 27, that leaves just two weeks of a mask-optional policy for toddlers in schools that are following the school calendar. Advisers to federal regulators are scheduled next week to weigh in on whether to authorize vaccines for children younger than 5, and the shots could be available as soon as the week of June 21.

The city’s latest wave of cases, driven by two Omicron subvariants, appears to have peaked on May 18, with an average of about 4,400 daily confirmed cases, according to city data. After several weeks of decline, case counts and hospitalization rates are now approaching the lower rates that would officially mark the city’s return to a “medium” or yellow alert level.

Nationally, new confirmed cases have been roughly flat at around 110,000 a day on average over the past two weeks as of Wednesday, according to a New York Times database, after rising from lower than 30,000 a few months ago. Infections, though, are thought to be widely underestimated. Death counts have been volatile in recent weeks but remain below 400 per day on average.

Parents who opposed the mandate reacted on Thursday with a mixture of relief and frustration that the rule lasted for so long. In New York City, masks are still required on public transit, in medical facilities and in some congregate facilities such as homeless shelters, according to city rules.