American biotech company Moderna said Thursday it was asking the US Food and Drug Administration for an emergency use authorization for its Covid-19 vaccine to be given to adolescents.

The move was widely expected after the company announced in May early results from a trial of 3,700 12-to-17-year-olds that found the two-dose regimen was safe and highly effective.

On Monday, Moderna made similar requests to the European and Canadian regulators.

"We are encouraged that the Moderna COVID-19 vaccine was highly effective at preventing COVID-19 and SARS-CoV-2 infection in adolescents," said the company's CEO Stephane Bancel.

Vaccine efficacy was shown to be 100 percent after two doses when using the same definition of symptomatic disease that was applied to the adult trial.

It fell to 93 percent after one dose when using a more stringent definition used by the Centers for Disease Control and Prevention that requires just one symptom in addition to a positive test.

No significant safety concerns were noted. The most common side effects outside the injection site after the second dose were headache, fatigue, body aches and chills.

The United States began inoculating teens -- like 13-year-old Charles Muro in Connecticut -- with Pfizer-BioNTech's Covid-19 vaccine in May 2021, and Moderna is now the second firm to seek a US green light to administer its shot to adolescents
The U.S. began inoculating teens -- like 13-year-old Charles Muro in Connecticut -- with Pfizer-BioNTech's Covid-19 vaccine in May 2021, and Moderna is now the second firm to seek a U.S. green light to administer its shot to adolescents. AFP / Joseph Prezioso

The FDA authorized the use of the Pfizer-BioNTech Covid-19 vaccine for children aged 12 to 15 years old in May.

Although adolescents are much less susceptible to severe Covid than adults, experts believe they are important to reach in order to help achieve population immunity against the disease.

The Moderna Covid-19 vaccine was developed in collaboration with the US National Institutes of Health using messenger ribonucleic acid (mRNA) technology.

It uses genetic material to deliver instructions to human cells to create the spike protein of the coronavirus, thereby training an immune response without exposing the host to a real infection.

The US has reached almost 52 percent of its population of 332 million with at least one dose, but its vaccination campaign is slowing in the face of hesitancy.

President Joe Biden has set a target of having 70 percent of adults vaccinated with at least one dose by July 4. The current figure is just under 64 percent, and the goal might be missed.

Coronavirus