What to know about the new COVID vaccine for kids under 5 

Canada's drug regulator, for the first time, has approved a COVID-19 vaccine for infants and preschoolers.

Health Canada announced on Thursday that the Moderna vaccine can be given to young children between six months and five years old, in doses one-quarter the size of that approved for adults.

The approval was based on review of clinical trial data from Canada and the United States, and means 1.7 million more Canadians will soon be able to get a vaccine against the COVID-19 virus.

Many parents have been waiting for this announcement, and many also have questions. 

CBC News talked with health experts to get answers. 

While the vast majority of young children who catch COVID-19 show only mild symptoms, some can develop more serious cases of the illness and require hospitalization. 

Hospitalizations among children under five rose considerably after the arrival of the Omicron variant in December.

According to the Public Health Agency of Canada, that rate climbed from 1.4 per 100,000 children between March 1, 2020, and Dec. 31, 2021, to 15.9 per 100,000 between Jan. 1, 2022, and March 31, 2022.

The vaccine gives parents an option that will help reduce that risk and provide strong protection against serious illness, said Dr. Katharine Smart, a pediatrician and the president of the Canadian Medical Association.

"Right now, one of the most common risks to children in terms of an infectious disease is COVID-19," she said. 

The clinical trial data, gathered after the arrival of Omicron, showed the Moderna vaccine prevented symptomatic COVID-19 at a rate of 50 per cent in children between six and 23 months of age, and at a rate of 37 per cent in children two to five years old.

It's not yet clear from the existing data whether the vaccine will help curb transmission, said Smart — although research on other age groups has demonstrated vaccines help in this regard. "We don't really have the data to answer it," she said.

The clinical trial data found fatigue to be the main side effect, along with irritability, crying, and pain at the injection site. 

Reactions were mild to moderate and disappeared a few days after the vaccination.