Moderna announced Tuesday that its coronavirus vaccine, which is only approved for use in adults, will be effective in 12-17 year olds and will apply to the Food and Drug Administration for approval to use the vaccine in June for adolescents.

If approved, the vaccine would be the second Covid-19 vaccine available to U.S. adolescents. Federal regulators this month approved the Pfizer BioNTech vaccine for 12 to 15 year olds.

The Pfizer shot was originally approved for people aged 16 and over, while Moderna was available for people aged 18 and over.

Evidence of the effectiveness and safety of youth vaccines will help school officials and other business leaders plan for fall. On Monday, Mayor Bill de Blasio said all public students in New York City, the largest school system in the United States, would study in person again this fall.

New York’s move comes as several states have indicated they will be restricting distance learning, including Connecticut, Illinois, Massachusetts, and New Jersey.

The Moderna results, which the company announced in a statement, are based on a clinical study that enrolled 3,732 people ages 12 to 17, two-thirds of whom received two doses of vaccine. There have been no cases of symptomatic Covid-19 in fully vaccinated teenagers, the company reported. That’s 100 percent effectiveness, the same number Pfizer and BioNTech put in a study of their vaccine in 12-15 year olds.

“These results seem promising,” said Dr. Kristin Oliver, pediatrician and vaccine expert at Mount Sinai Hospital in New York. “The more vaccines we have to protect young people from Covid, the better.”

Moderna also reported that a single dose of its vaccine had 93 percent effectiveness against symptomatic diseases.

“The cases that occurred between the two doses were mild, which is also a good indicator of disease protection,” said Saskia Popescu, an infectious disease epidemiologist at George Mason University, in an email.

Side effects were consistent with reports in adults: injection site pain, headache, fatigue, muscle pain, and chills. “So far, no significant safety concerns have been identified,” the company said.

The adolescents in the study will be monitored for one year after their second dose.

The results were announced in a press release that did not include detailed data from the clinical trial. And Dr. Rasmussen said the vaccine’s effectiveness is more difficult to assess in children, who are less likely to develop symptomatic disease than adults.

Still, she said, the results are in line with the scientists’ expectations, suggesting that “adolescents react to the vaccine in a similar way to adults who receive it.”

Moderna said it plans to submit the data for publication in a peer-reviewed journal.