The Moderna COVID-19 vaccine for kids between the ages of six months and five years has been authorized by Health Canada, making it the first shot to be offered to young children.

Many parents are breathing a sigh of relief, in anticipation of what is likely to be the final leg of Canada’s age-based vaccination effort. Making shots available to an age group that had previously gone unprotected will also play a role in slowing the spread of the virus more broadly, experts say.

The vaccine is one quarter the size of the adult dose, and will be given as two shots spaced four weeks apart.

The National Advisory Committee on Immunization is expected to provide recommendations later Thursday, though the actual availability of the shot will be determined by the provinces.

Health Canada based its decision on a study of more than 4,000 children that showed a similar immune response to that seen in young adults. While side-effects such as irritability, crying and loss of appetite were common, the regulator said no serious health effects were reported.

The decision to vaccinate is one parents will have to make for each child. While the data suggests kids haven’t gotten as sick with COVID as older adults, they have fallen ill. An international study published in an academic journal known as the JAMA Network in January tracked children in 10 countries who had turned up to the emergency room with COVID. According to the study, 3.3 per cent of those kids had a serious outcome in the next two weeks, meaning anything from intensive interventions to severe organ impairment or death. Of the 3,222 kids enrolled, four died.

There are some questions remaining, Health Canada notes. The long-term safety and efficacy data and the rate of very rare events such as myocarditis and pericarditis aren’t yet clear. While no incidents of those rare side-effects were found in trials, that could change as the shot is rolled out to more people.

In mid-June, the United States became the first country in the world to authorize vaccines for their youngest citizens. In a statement, U.S. President Joe Biden called the green light a “monumental step forward” in the fight against the virus.

“For parents all over the country, this is a day of relief and celebration,” the statement read.

But in comparison to previous rollouts, which were marked by long lineups of people eager to roll up their sleeves, this latest campaign has been more subdued, the New York Times has reported.

This time around, some parents have encountered misinformation about the shots, but others have either resigned themselves to living with the virus or have kids who have already been infected, dulling the sense of urgency to get protected, the paper reported.

Many experts still say there is a strong argument for getting kids under five vaccinated. The risk for getting serious COVID is lower than adults, but they have felt the impact of the pandemic nonetheless, says Alan Bernstein, president of the research organization CIFAR and member of the federal government’s COVID-19 vaccine task force.

The pandemic has also taken a serious toll on the mental health of children, and the more people get vaccinated, the better chance of slowing the progression of the virus, he added. (While the vaccines have proven less effective at preventing transmission against newer strains such as Omicron, they remain good at keeping people out of hospital.)

“I can understand the parents’ dilemma and trying to balance those things,” he said, speaking in advance of the regulatory decision. “On balance, my own view would be if I had a child under five, I would get them vaccinated.”