A pediatric infectious disease doctor is encouraging parents to get their young children vaccinated against COVID-19 now that a vaccine has been approved for this age group.

On Thursday, Health Canada announced Moderna's Spikevax vaccine has been approved for children aged six months to five years in doses one-quarter the size of the adult shot. It's the first COVID-19 vaccine approved for children under five in Canada.

Dr. Karina Top, an associate professor of pediatrics and community health and epidemiology at Dalhousie University, says it's exciting news. She said the risks of COVID-19 in young children are similar to adults.

"They can get quite sick and need to be hospitalized or need oxygen. Children also can get a condition called multi-system inflammatory syndrome, or they can get very high fevers and inflammation of their heart, and that can affect how their hearts working, as well as inflammation of other organs."

As of Tuesday's COVIDWatch report, a child under 10 was among the 15 New Brunswickers newly admitted to hospital in the past week, according to the province.

While most children fare well with COVID-19, Top said record numbers across the country have been hospitalized with Omicron.

According to the National Advisory Committee on Immunization, the average monthly rate of hospitalization for infants and preschoolers previously ineligible for COVID-19 immunization increased from 1.4 to 15.9 per 100,000, compared to the first two years of the pandemic.

"And many of the kids in the hospital were healthy, no other risk factors for getting hospitalized," said Top. "So you can't really predict whether your child's going to have a complication from COVID or not."

New Brunswick has not yet announced its vaccine rollout plan for this age group, but Dr. Jennifer Russell, the chief medical officer of health, told CBC news last month that the province would be ready as soon as a vaccine was approved.

The Department of Health did not respond to questions about how soon vaccinations will be offered or where, or how many children are eligible.

In a statement, spokesperson Valerie Kilfoil said the department has been working with its primary care partners, including the Horizon and Vitalité health networks, the College of Pharmacists, the New Brunswick Pharmacist Association, community pharmacies and the New Brunswick Medical Society "for some time now in anticipation of the approval of a vaccine for children aged six months to five years old."

"Guidance will be provided to immunizers for under five vaccinations. This includes sharing information from Health Canada, the vaccine supplier, NACI and guidance from New Brunswick Public Health."

The vaccine requires two doses. Moderna has recommended they be administered four weeks apart. But NACI recommended a dosing interval of at least eight weeks.

A primary series of three doses may be offered to young children who are moderately to severely immunocompromised, with four to eight weeks between each dose, NACI said.

For children who have already had COVID-19, NACI suggests waiting eight weeks after the start of COVID-19 symptoms or a positive COVID-19 test before beginning or continuing the primary series. This interval may be shortened to four weeks for children who are moderately to severely immunocompromised, NACI said.

Even if a child has already been infected, that doesn't mean they won't get COVID again and be more severely affected, said Top, noting new variants continue to emerge.

Young children can also spread the infection to other people in their home who may be at higher risk of getting really sick, she said.

"So, you know, sort of overall in terms of helping us to reduce the strain on the health system and keep young children healthy in daycare, in school, and our community safer … it's going to be really important."

During the trials on young children last winter, the vaccine was about 50 per cent effective against symptomatic COVID, including Omicron.

Top expects the effectiveness, as with other age groups, will be much higher in terms of preventing severe illness.

Meanwhile, adverse reactions to the shot during trials were generally mild and short-lived, such as sore arms, redness, swelling, fever and fatigue, she said.