TORONTO -- COVID-19 variants of concern continue to push hospital ICUs to maximum capacity and are the driving force behind several provinces' recent imposition of harsher restrictions for the public.
Generally, they’re also infecting a younger cohort of patients than the initial strains of the coronavirus.
While in the initial two waves of COVID-19 cases among children and adolescents were low, the recent surge of variants could change who contracts the virus in Canada, said clinical researcher and Toronto physician Dr. Iris Gorfinkel.
“What are we seeing? An increase in hospitalization and increase in ICU? And why is that? Because the variants are so much more contagious,” Gorfinkel said in a telephone interview with CTVNews.ca on Wednesday. “So that leads to the logical question: could new variants do the same in kids?”
“Right now, no one's even asking that question,” she continued. “But the fact of the matter is, we have seen variants change the trajectory of what we've seen in the past. We cannot assume that it's always going to act the very same way.”
Last week, Health Canada’s chief medical adviser Dr. Supriya Sharma said in a Facebook Live session that Pfizer’s COVID-19 vaccine will “likely” be the first to be administered to younger teens, something Gorfinkel says is welcome news.
“Those 19 years of age and under represent 20 per cent of Canada's population. So it is impossible - emphasis on the word impossible - to achieve herd immunity without them,” she said.
Gorfinkel said that it’s estimated that herd immunity “kicks in” when about 90 per cent of the population is vaccinated, so even if Canada had “100 per cent compliance” within the populations eligible to get inoculated, the country would not achieve herd immunity.
“Every child who carries the virus has the potential to create a variant of concern,” Gorfinkel said. “That's why every single case in Canada matters.”
WHERE DO VACCINES STAND RIGHT NOW?
In a March 31 news release, Pfizer and BioNTech said that their COVID-19 vaccine “BNT162b2” is safe for adolescents and “demonstrated 100 per cent efficacy” in preventing the disease and “robust antibody responses” in a Phase 3 trial in participants aged 12 to 15 years-old in the U.S.
The U.S. Food and Drug Association and Health Canada have yet to review the study findings.
“We plan to submit these data to the FDA as a proposed amendment to our Emergency Use Authorization in the coming weeks and to other regulators around the world with the hope of starting to vaccinate this age group before the start of the next school year,” chairman and CEO of Pfizer Albert Bourla said in the release.
The Pfizer vaccine has been cleared for use in people as young as 16 in Canada, and Sharma said that Canada will review the Pfizer-BioNTech’s data on 12- to 15-year-olds “in a couple of weeks,” with Health Canada reviewing the full data on adolescent use, including on children aged six to 12, in a few months.
Sharma said they would use “bridging data” from earlier trials to make sure the vaccines are safe and effective for children.
Moderna is conducting a clinical trial in Canada for children aged five to 11, with results expected early next year. Another trial in infants aged six months to under 12 years-old was launched in the U.S. in March.
Johnson & Johnson, whose “one-shot” vaccine for adults was approved for use on adults in Canada in March, with the first shipment expected to arrive at the end of April, expanded a Phase 2 trial to include children aged 12 to 17, with plans to include younger subjects down the line.
AstraZeneca launched a trial in February to assess the safety and efficacy of their vaccine in young adults aged 6 to 17 years-old, however the trial was paused Tuesday pending a safety review of blood clot cases by U.K. regulators. The adolescent trial was not paused because of safety concerns in the trial, but to allow the wider review to finish, a statement provided to U.K. media said.
In China, Sinovac recently announced it had submitted preliminary data to Chinese regulators showing its vaccine is safe in children as young as three years old. Sinovac is not approved for use in Canada.
The list of COVID-19-related clinical trials for drugs and vaccines authorized by Health Canada can be found on their website.
WHAT DO THE VACCINE TRIALS LOOK FOR?
Gorfinkel said that children under the age of 10 are half as infectious as adults and are less likely to transmit the disease. However, once they reach 10 to 15 years of age, children are just as contagious as adults are.
As of March 26, 2021, the Public Health Agency of Canada lists 163,514 cases of COVID-19 in adolescents aged 19 and under, 17.3 per cent of the 944,743 cases where detailed case data was provided.
Just over 800 of those cases in adolescents required hospitalization.
When it comes to vaccine trials, “virtually all” of the major companies are looking at the safety and efficacy of the vaccines for children.
“The good news is they don’t have to repeat the entire trial…they don’t have to repeat all the same research,” Gorfinkel said. “Basically they’re looking at how tolerable the vaccine is to kids as kids tend to have a more robust immune system…they're checking the antibody levels to ensure that these antibodies that are specific against COVID-19 are robust enough and staying put enough, and they're also looking at safety.”
Trials will generally start with an older cohort of children, and once results have proven to be safe and effective, will drop the age of trial participants and “go down slowly.”
“Taking it slowly and making sure you understand the facts before moving on to a younger population as younger populations introduce potentially very different immune responses,” Gorfinkel explained, adding that if a younger child in the trial triggers a certain immune response, that can inform researchers on dosage values per age group and how the trial continues.
Children in the Pfizer-BioNTech clinical trial reported side-effects similar to the ones described by adults: pain at the injection site, headaches, fever and fatigue.
But Gorfinkel decried the lack of mining “head-to- head” data on COVID-19 cases and vaccines in Canada by health authorities, something essential when understanding how different populations will react to the virus and inoculation – children included.
“I'm very concerned that we are failing in Canada to mine our data like we should,” she said. “We're given case counts, we have data on ICUs, we have data on hospitalizations - how come there is no national vaccine registry in which we are not overlaying that data with all of the testing data?”
“It is completely and utterly ridiculous to me that we're not doing that.”
Gorfinkel acknowledged that the pandemic presented an “emergency situation” that changes rapidly, but said Canada has no data “on which vaccine is the best” for different age groups.
“Patients are asking me every day, and you know what? We don’t know…because the data is not comparable, there’s no head-to-head data telling us which vaccine is the best…and with the variants of concern we are going to be in deep trouble unless we start mining our data,” she said. “There’s people at NACI, people at the Public Health Agency of Canada who can do this.”
Relying on data from other countries isn’t feasible either.
“Canada is not the same as the U.K., we have a very different population, a very unique set of populations,” Gorfinkel said. “There could be very significant differences that change the trajectory of how we see rare adverse side effects of efficacy against emerging variables of concern.”
“There is no good substitute for looking at your own data in a hard way.”
