Canada weighs need for third shots
Israel, Germany, U.S. planning boosters
The U.S. government is planning a massive COVID-19 booster shot rollout this fall, warning that data “make very clear” that protection against the pandemic virus ebbs over time.
How long should authorities in Canada wait before deciding who should get a third shot, and when?
American health officials cautioned Wednesday “the current protection against severe disease, hospitalization and death” for the vaccinated could diminish in the months ahead, particularly for the elderly and those vaccinated in the early days of the vaccine rollout. If green-lit by drug regulators, booster shots for all Americans who desire them could begin in late September, starting at eight months after a person’s second dose.
Israel and Germany have already announced plans to boost the vaccinated over concerns of waning immunity. Canada’s independent body of vaccination advisers is mulling the need for booster doses, while Ontario has already pledged third shots for long-term care residents, organ transplant recipients and others considered at high-risk of “breakthrough” infections — cases that occur 14 days or more after the second vaccine dose.
Most vaccinated Canadians are only a few months out from their second shot. While the authorized vaccines are remarkably effective in helping keep people from being hospitalized or dying, and most cases of severe COVID are occurring in the unvaccinated, the highly contagious Delta variant “will cause a lot of mild and asymptomatic infections even in vaccinated people,” said immunologist Dawn Bowdish.
The question for Bowdish: What’s our end game, here? “Are we going to try to make sure that we reduce those asymptomatic and mild infections in vaccinated people? Then maybe a booster is helpful,” said Bowdish, a professor of medicine at Hamilton’s Mcmaster University and Canada Research Chair in aging and immunity. “Or maybe we need to hold out and wait for the clinical trials of variantspecific vaccines.”
She and others worry calls for booster shots and nervousness over breakthrough cases in the fully vaccinated will increase vaccine skepticism. “I’m getting an earful from the vaccine hesitant group — ‘See, your vaccines don’t work.’”
What matters more are breakthrough infections that make people sick or, in rare cases, send them to hospital, Bowdish said. Not breakthrough cases, which are mostly mild or asymptomatic.
Nationally, of the 12.6 million people who had achieved “full vaccination” status as of July 24, 3,417, or 0.03 per cent, were diagnosed with COVID while fully vaccinated, according to the Public Health Agency of Canada.
Still, a July outbreak of COVID in Provincetown, Mass., led the U.S. Centers for Disease Control and Prevention to walk back its mask stance for the fully vaccinated. Of 469 people infected in the Provincetown cluster following “multiple large public gatherings,” 74 per cent occurred in fully vaccinated people, meaning those who had completed a two-dose regimen of Pfizer or Moderna, the MRNA vaccines, or a single jab of the Johnson & Johnson shot. Among five people who were hospitalized, four were fully vaccinated; no deaths were reported. The viral loads of the vaccinated and unvaccinated also seemed similar, suggesting they were equally likely to infect others, prompting the CDC to urge the fully vaccinated to mask again indoors in areas with high COVID infection rates.
Other studies suggest viral loads drop faster in vaccinated people who catch the Delta variant, meaning they remain infectious for shorter periods than the unvaxxed with Delta.
Iceland, with 71 per cent of its population totally vaccinated, is seeing a surge in COVID infections, many among the vaccinated. But hospitalizations and deaths have remained low, The Washington Post reported. On Wednesday, there were 25 people in hospital with COVID. The country’s COVID outbreak “would be catastrophic” without vaccines, Pall Matthiasson, chief executive of Iceland’s largest hospital, told the Post.
Bowdish, together with Andrew Costa — both researchers with Canada’s Global Nexus for Pandemics and Biological Threats — said she found that, among long-term care residents, by five months post-vaccination, “these folks are dropping antibody levels to the point where we would not predict them to be protected,” making boosters urgent for the most vulnerable. “We’re just starting to see those breakthrough infections coming through in those folks,” Bowdish said.
The perfect vaccine causes sterilizing immunity. None of the current vaccines provide sterilizing immunity against COVID-19 or Delta.
“If you look at the modelling, we expect a world now where we all get Delta at some point,” Bowdish said. “You’ve got two choices: you can get Delta when you are vaccinated, in which case you’ll probably be asymptomatic or have mild symptoms. Or you get infected without being vaccinated, in which case you may have long COVID, you may end up in the ICU and you may have long-term health issues.”
“The choice we have as individuals is, what do we want those infections to look like?”
As for boosters, what matters is time-since-dose — “you want to get your timing right,” Bowdish said — balanced with Canada’s international responsibilities. The World Health Organization has accused rich countries of letting the rest of the world burn by buying up all the booster shots, Bowdish said. The more people infected globally, allowing the virus to propagate, the greater the probability of new and more dangerous variants.
“On the other hand, politically, of course, we have to protect our own,” Bowdish said.
The time for boosters likely isn’t now for Canada, at least not for the general population, she said. Most have been recently vaccinated. “And, to be frank, we have a huge mixed bag of vaccine types. Some of those, any immunologist would tell you, probably have longer lasting effects than others.”
In the long-term care study, Moderna stimulated a stronger immune response in frail, older adults. Moderna uses three times the MRNA. It’s probably the reason there are more symptoms associated with Moderna in younger adults, Bowdish said — “it’s surplus to requirements,” because younger people have stronger immune systems. In older people, more is better. But Bowdish doesn’t want the take-away to be one is better than the other. Pfizer of Moderna, “they’re equally good.”