The US Food and Drug Administration granted emergency authorization Friday for the use of Pfizer and Moderna COVID-19 vaccines in the youngest children, the final age group awaiting immunization in most countries.

The agency, whose approval is considered the global gold standard, authorized Moderna's two-dose vaccine for children aged six months to five years, and three doses of Pfizer's shots for those between six months and four years old.

"Many parents, caregivers, and clinicians have been waiting for a vaccine for younger children and this action will help protect those down to six months of age," FDA chief Robert Califf said in a statement.

"We expect that the vaccines for younger children will provide protection from the most severe outcomes of COVID-19, such as hospitalization and death."

Pfizer said it plans to submit requests for authorization to other regulators around the world, including the European Medicines Agency in early July.

"Parents in the US now have the option to vaccinate their children under 5 years of age, and we are working to ensure that other countries worldwide will follow," said Ugur Sahin, CEO, and co-founder of Germany's BioNTech, which developed the vaccine together with Pfizer.

The Centers for Disease Control and Prevention (CDC) must now also recommend the vaccines before they are put into use in the United States – a final green light that will be given after a meeting of an advisory committee of experts that is expected to be held shortly.

But the government has said that as soon as the FDA decision was made, 10 million doses could immediately be sent around the country, followed by millions more in subsequent weeks.

Successful trials

Both vaccines are based on messenger RNA, which delivers genetic code for the coronavirus spike protein to human cells that then grow it on their surface, training the immune system to be ready. The technology is now considered the leading COVID vaccination platform.

The vaccines were tested in trials of thousands of children. They were found to cause similar levels of mild side effects as in older age groups and triggered similar levels of antibodies.

Efficacy against infection was higher for Pfizer, with the company placing it at 80 percent, compared to Moderna's estimates of 51 percent for children aged six-months to two years old and 37 percent for those aged two to five years.

But the Pfizer figure is based on very few cases and is thus considered preliminary. It also takes three doses to achieve its protection, with the third shot given eight weeks after the second, which is given three weeks after the first.

Moderna's vaccine should provide strong protection against severe disease after two doses, given four weeks apart, and the company is studying adding a booster that would raise efficacy levels against mild disease.

However, Moderna's decision to go with a higher dose is associated with higher levels of fevers in reaction to the vaccine compared to Pfizer.

"We are thrilled that the FDA has granted Emergency Use Authorization of Moderna's COVID-19 vaccine for children and adolescents, particularly for our vulnerable, youngest children," said Moderna CEO Stephane Bancel.

"Children need to live highly social lives to develop and flourish," Bancel added. "With this authorization, caregivers for young children ages 6 months through 5 years of age finally have a way to safeguard against COVID risks in classroom and daycare settings."

The United States, home to 20 million children four years and under, has recorded 480 COVID deaths in that group in the pandemic – far higher than even a bad flu season, according to the FDA.

As of May 2022, there have been 45,000 hospitalizations in that group, nearly a quarter of which required intensive care.

© Agence France-Presse