Eight months since the first COVID-19 vaccines began rolling out in Canada, safety and efficacy of the shots among babies and younger children are still being investigated.
In Canada, so far only Pfizer-BioNTech’s COVID-19 vaccine has been authorized for use in children aged 12 years and above. Moderna submitted its application for approval to Health Canada in June.
But kids under 12, including toddlers, are waiting for their turn as a number of clinical trials are under way.
Vaccinating this group will enable a safer reopening of schools, a return to normalcy as well as control the disease’s spread to more vulnerable adults, experts say.
“Kids are largely asymptomatic and so they will be transmitting the virus and they’ll remain reservoirs of the virus,” said Fatima Kakkar, a pediatric infectious diseases physician at CHU Sainte-Justine in Montreal.
While children are less likely to experience serious symptoms of COVID-19, the disease is not entirely benign in them, she told Global News.
“We do have cases of what we call the post-COVID syndrome, multisystem inflammatory syndrome, which can be quite severe, bring kids to the hospital, the intensive care unit. And so for their own health themselves, (the vaccine is) important.”
How do the children’s trials work?
Human testing in clinical trials are divided into three phases. Phase 1 and 2 trials involve 10 to 100 healthy volunteers and focus on adverse events and immune response.
Phase 3 trials recruit thousands of participants, where they receive either the vaccine or a placebo.
It is only the Phase 3 trials that can provide a pivotal demonstration that a vaccine both works and is safe, according to Charles Weijer, a bioethicist at the Western University.
Children also undergo three phases of the vaccine trials, but the sample size is not as large.
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Because the efficacy of vaccines has already been tested in large-scale clinical trials among the adult population, the same steps are not needed for children.
“Some of the work has been done already in adults, so you don’t need to have 40,000 people to prove that the vaccine works,” said Anna Banerji, a pediatric infectious diseases specialist at the University of Toronto.
Instead, the pediatric trials focus on the specific dosage needed. These are called dose escalation studies.
“We want to use the lowest amount of dosage possible to produce the immune response which will result in protection against severe COVID,” said Kakkar.
Why do children need separate trials?
The biggest burden of COVID-19 disease has been on the elderly, who are at a higher risk of hospitalization and death.
Because there was a greater urgency to vaccinate the seniors and adult population, children were not included in the initial stages of the COVID-19 vaccine trials.
Another reason for the exclusion was safety.
“We wanted to make sure that the vaccines were safe in adults, first of all, before applying them for use in children,” said Jesse Papenburg, a pediatric infectious disease specialist and medical microbiologist at the Montreal Children’s Hospital of McGill University Health Center.
Children tend to have a much stronger immune response than adults, which is why they can’t be given the same dose as adults, because they might react at a much higher level, said Kakkar.
Papenburg said because children are smaller they oftentimes don’t need as large a dose to elicit a good immune response.
Side effects
According to data from the Pfizer’s Phase 3 trials conducted in adults, which included over 2,000 participants between 12 and 15 years of age, the safety profile of the vaccine in the adolescents was similar as for older people.
“The most commonly reported side effects were temporary and mild, like a sore arm, chills or fever,” Health Canada’s chief medical advisor Dr. Supriya Sharma said during a May 5 press conference.
A peer-reviewed study published in the New England Journal of Medicine on July 15 found that the Pfizer vaccine in 12-to-15-year-old recipients had a favorable safety profile, produced a greater immune response than in young adults, and was highly effective against COVID-19.
In general, young adults and adolescents tend to experience more side effects, which are brief and easily manageable, said Papenburg.
Meanwhile, there have been reports of heart inflammation after COVID-19 vaccines predominantly among male adolescents and young adults in the United States and Israel.
Banerji said while the cases of myocarditis and pericarditis were mild and rare, they should be monitored closely.
As for younger kids, Kakkar said there haven’t been “any major signals or safety concerns coming out of the Pfizer or the Moderna trials.”
When will kids under 12 get a vaccine?
Both Pfizer and Moderna started trials of their COVID-19 vaccines for children under the age 12 years in March.
According to the drug makers, results are expected in the fall. But before the shots can be doled out, Health Canada has to review the applications.
Back in May, Health Canada’s Sharma said that Pfizer had signalled that they may be giving the agency a submission for the younger age groups of five to 11 “as soon as September”.
If the data looks good, then Canada could potentially have a COVID-19 vaccine approved for use for that age group as early as fall.
Trials are also under way for children aged two to four, but those results are not expected until the end of the year, said Papenburg.
“For infants, we’re probably looking at the first or second quarter of 2022,” he added.
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