Moderna has applied for Canadian approval of a third dose of its COVID-19 vaccine, the company announced Tuesday.
This comes as other countries, including the U.S. and Israel, have approved or even required COVID-19 vaccine booster shots for large portions of their population — but experts remain divided on how much it will help.
Moderna says the booster will be necessary.
“We’ve seen this huge emergence of a Delta surge this year and that’s intersecting with many people being almost a year out of their primary vaccination,” Moderna president Stephen Hoge told Global News in a recent interview.
“And what we know is you’ll see waning immunity, decreasing neutralizing titers in the blood of people at about a year. So we do think it’s about time for a booster so that we can get to the highest levels of protection possible given the ongoing surge.”
Health Canada has to review the application and will choose whether to approve the booster shot and under what conditions. There is no timeline for how long this could take.
The booster shot will contain 50 micrograms of active ingredient, the company said – half of what is in the initial two doses. This is in line with the similar request that Moderna has submitted to the U.S. FDA.
Other than being a half-dose, the vaccine will be the same formulation as the original vaccine, Moderna says.
“At present, we really do believe the prototype vaccine, the original vaccine, is going to protect against all the current variants,” Hoge said.
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Are booster shots needed?
Many scientists remain unconvinced that the average Canadian will need a COVID-19 booster shot anytime soon, saying we’re not yet seeing a decline in the protective effect of existing vaccines.
“I think that a booster dose is needed when you see a decline in protection,” said Dr. Gaston De Serres, an epidemiologist practitioner at the Institut National de Santé Publique du Québec who has been examining Canada’s COVID-19 data. “This happens with some vaccines and there is need then to get a booster dose. But in our data at this time, we see pretty much no decline in protection.”
Recent data from Quebec shows that all three vaccines — Moderna, Pfizer and AstraZeneca – remain highly effective against infections, and are even more effective against hospitalization.
Reports from the B.C. Centre for Disease Control come to a similar conclusion, showing the vaccines are 80-90 per cent effective against infection, even months after the second dose.
“All of the products perform outstandingly well,” said Dr. Danuta Skowronski, the epidemiological lead for the BCCDC.
“Taking it out to five plus months since the second dose, we’re not seeing an indication of waning in the general population of B.C. overall,” she said, adding that the protection remains “outstanding” even against the Delta variant of COVID-19.
Alyson Kelvin, a vaccinologist and scientist with the Vaccine and Infectious Disease Organization at the University of Saskatchewan, also doesn’t yet see the evidence for booster shots.
“Right now, the data doesn’t quite support booster shots for the general population — that’s in my expert opinion,” she said. “We don’t have enough evidence to show waning immunity as well as decrease in protection from hospitalization from COVID in people who are vaccinated.”
However, a study released Tuesday on the Pfizer-BioNTech vaccine suggests that this vaccine’s effectiveness does eventually wane. The study, based on data from California, found that the vaccine’s effectiveness against infection dropped to 47 per cent from 88 per cent after six months. Protection against hospitalization remained high however, at 90 per cent over at least six months.
Adding a third dose can also bring a risk of side effects. Both mRNA vaccines are associated with a risk of pericarditis/myocarditis, an inflammation of heart tissues, particularly among young men. But the risk is higher with Moderna’s vaccine than Pfizer’s. While the condition is relatively rare, Ontario now recommends that people aged 18-24 be offered the Pfizer vaccine instead.
Moderna isn’t sure whether the myocarditis risk will increase with a booster shot, Hoge said.
Because these events are extremely rare, they don’t show up in their clinical studies, he said. “We’re talking about less than one hundred per million people in those age groups being given a vaccine. And so you really won’t see them in clinical studies.”
The company did not see higher rates of other side effects after a third dose in clinical trials, he said.
The National Advisory Committee on Immunization (NACI) has already recommended third doses of Pfizer and Moderna’s vaccine for certain immunocompromised individuals who did not mount a sufficient immune response to the usual two-dose regimen. This is considered to be part of the primary vaccination series for these individuals, and not a booster shot.
NACI has also recommended that a booster dose of mRNA vaccine be given to residents of long-term care homes and seniors living in other congregate settings, at least six months after they received their second dose.
NACI is still examining whether booster shots should be given to the broader population. Some provinces are also offering third doses to individuals who received mixed types of vaccine, or vaccines not currently approved in Canada, so that they can meet requirements for travel to certain countries.
Other countries have embraced booster shots, however. Israel recently amended its vaccine passport to require that people receive a booster shot in order to access indoor venues like restaurants or gymnasiums.
The FDA has approved Pfizer booster shots for Americans aged 65 and older, as well as individuals at high risk of COVID-19, or people working or living in high-risk settings — like health care workers — that put them at risk of developing severe COVID-19.
Moderna sent initial data on COVID-19 boosters to the U.S. FDA on Sept. 1. The FDA’s advisory committee is set to meet Oct. 14-15 to discuss booster doses of the Moderna and Janssen vaccines.
More than 4 million Canadians have received at least one dose of Moderna’s vaccine, according to statistics from the Public Health Agency of Canada.
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