Health Canada’s chief medical adviser says variant-specific vaccines can be approved faster than the general ones first issued to combat COVID-19, but one targeting the Omicron strain still likely won’t be ready in time to help with the latest wave.
Dr. Supriya Sharma said what is really needed are vaccines that can possibly stop more than one variant at a time, including those yet to come.
Omicron became the dominant variant in Canada in just over two weeks, and the Public Health Agency of Canada said Friday it’s now believed to be responsible for more than 90 per cent of all COVID-19 cases.
Studies suggest two doses of the existing mRNA vaccines from Pfizer-BioNTech and Moderna are not good at preventing infection from Omicron.
Multiple studies, however, suggest the vaccines are excellent at keeping symptoms mild, preventing hospitalizations, and shortening the stay and lowering the level of care for those who do get admitted to hospital. Fewer vaccinated Omicron patients, for example, need mechanical ventilation.
Both Pfizer and Moderna are working on new versions of their vaccines that specifically target the Omicron variant.
Moderna is hoping to get its product into trials early this year. Pfizer said it could have 100 million doses of theirs ready as early as March, and Canada has contracts for boosters from both companies that would include vaccines for variants too.
But Sharma said even with the expedited review process for vaccine variants, that’s “probably not” fast enough.
“By that time, based on what we’ve known about the Omicron wave, it might well and truly be through,” she said. “And then the question is always, ‘is there another variant that’s coming up?’”
The solution, she said, likely lies with vaccines that can target more than one variant at a time.
The COVID-19 vaccine technical committee of the World Health Organization said the same thing on Jan. 11, noting Omicron is the fifth variant of concern in two years and “is unlikely to be the last.”
Booster shots that heighten antibody development became the immediate response to Omicron for many governments, including Canada.
Dr. Srinivas Murthy, a British Columbia pediatrician and co-chair of the WHO’s clinical research committee on COVID-19, told The Canadian Press that boosters aren’t a long-term viable option.
“Boosting your way out of a pandemic is going to inevitably shoot you in the foot in the sense that you’re going to have a future variant that’s going to emerge that’s going to cause problems,” he said. “It’s going to evade your vaccines, and then you’re going to have to scramble.”
Omicron doesn’t evade the existing vaccines entirely but a future variant could, he said. The issue largely stems from the fact that the original vaccines train the body’s immune system to recognize what is called the spike protein found on the surface of a virus, and that spike protein is mutating significantly.
Think of the mutated spike protein as a bit of a disguise that makes it harder for the immune system to recognize the virus and mount a defence to kill it off.
Omicron has more than 50 mutations, and at least 36 are on the spike protein.
Multivalent vaccines that use the spike protein from more than one variant, or that target the genetic components of a virus rather than the spike protein, are possibly the ones that could offer protection for both this pandemic and the next novel coronavirus that emerges.
“It’s pan-coronavirus, where it’s looking at big broad neutralizing responses and you don’t have to update it every season and so on,” said Murthy. “That’s been the Holy Grail of flu vaccinology for the past number of decades. We haven’t achieved that yet, because flu is a bit tricky, but we think that it’s achievable for coronavirus, specifically.”
The United States Army has a version heading into Phase 2 trials that can attach multiple spike proteins. A vaccine with the specific spike proteins from all five COVID-19 variants of concern would likely be more successful, even against future variants, because they all share some of the same mutations and what one might miss another may catch.
Moderna is working on trials for multivalent vaccines using combinations of the spike proteins from the original virus and one of the variants, or two of the variants together. It’s not clear when they would be ready for use.
Sharma said even if the vaccines aren’t working as well against variants as they were against the original virus, to her “they’re still miraculous.”
“To have a vaccine that was developed that quickly, that still has, through multiple variants … with boosters, up to 70, 80 per cent effectiveness against serious disease, ailments, hospitalization and death,” she said. “That is miraculous for a new vaccine for a new virus.”
Mia Rabson, The Canadian Press
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