Vaccine boosters may be needed by spring
With the provinces still hurrying to get second COVID vaccine doses into bodies, it seems odd to be talking boosters, third doses. Can’t we just celebrate this moment, of “sustained national decline” in COVID and glorious reopenings, and catch our breath?
Most Canadians have been, or will be, getting second dosed from May through July, and published data suggest “very little drop off” in antibody levels by several months out, said University of Toronto immunologist Tania Watts. Unlike the United Kingdom, which, according to the BBC, is planning for an autumn “booster jab” rollout, Watts very much doubts the Canadian general public would need a third dose in the fall.
Beyond that, the situation gets murky. “If we need it, could it be as early as next spring? Possibly,” she said. Two or three years? Again, possibly. These are new vaccines and a new virus and it’s hard to predict. But assuming immunity will, at some point, wane, “I think there has to be an option to be ready to roll out the vaccine again,” Watts said.
The World Health Organization estimates boosters will be needed yearly for the most vulnerable, and every two years for the general population, according to an internal document seen by Reuters. An independent group advising the U.S. Centers for Disease Control and Prevention, however, isn’t yet swayed booster shots are necessary, though Moderna and Pfizer are already trialling third doses of their formulas.
While more data are needed, talk of boosters is also raising the issue of vaccine hoarding. Canada has committed more than $1 billion to buy up to 282 million doses. Do we store those extra shots for third doses, or help the world’s poorest countries get theirs first?
“I think we’ve got, what? Six or seven times what we need for our country,” Watts said. “Once we have everyone vaccinated there is a thought that we should definitely make sure we contribute to the world vaccination effort.” Because as long as the virus is circulating extensively in other parts of the world, new mutations and variants will arise and be brought into Canada by people coming into our midst.
“At the same time, we don’t want to start from zero again if we need boosting,” said Watts. The vaccines are good. A vaccine with 90 to 95 per cent protection after two doses is exceptionally good, she said. But just how durable that immunity is remains a bit of a black box.
Several thousand people are enrolled in a U.K. trial testing the effects of a third dose on people’s immune responses. Researchers are testing seven different vaccines to determine whether three is better than two. Early results are expected in September.
Boosters are also an issue for Canada’s national COVID19 immunity task force. “People are getting their second shot, and getting the peace of mind that comes with knowing that you’ve got good protection against hospitalization and severe disease and death,” said Dr. Catherine Hankins, co-chair of the task force and a professor in McGill University’s School of Population and Global Health. But the science is evolving. “We don’t know is that good for six months? Is it good for two years?”
Twenty-six per cent of eligible Canadians are now fully vaccinated and the country is seeing a “strong and steady decline” in disease, Canada’s chief public health officer, Dr. Theresa Tam, told a Friday press briefing.
COVID’s Delta variant, however, is worrying, because it appears to be escaping some immunity from vaccines, and, according to the modelling, may result in a greater than originally expected fall or winter surge.
But it’s not clear what evidence should be used in deciding if — or when — boosters might be needed, Hankins said. Tracking breakthrough infections in people who were fully vaccinated? Is it because of a variant or waning immunity? Scientists are trying to get a deeper understanding of the thresholds, or correlates of protection, the level of neutralizing antibodies required to protect from COVID. “We think that having antibodies is a good sign. We haven’t exactly figured out what level you need,” Watts said.
And who would need this annual booster? “If you had to prioritize, you’d want your most vulnerable people, the ones that have more difficulty mounting an immune response,” Hankins said, including older people, long-term care residents, the immune compromised and people with transplanted organs.
The issue of storing versus sharing arises not only for boosters, but also for the under 12’s. Vaccines for children under 12 could be available in the fall, depending on the outcome of ongoing trials, but is it morally defensible to be vaccinating children in richer nations, while the pandemic rages in other countries, threatening the elderly, health-care workers and other vulnerable populations while increasing the risk of new variants being spun off?
“It’s a huge debate. The pediatric one is hot now,” Hankins said. WHO estimates 11 billion doses will be needed to vaccinate 70 per cent of the world’s population to end the pandemic, without even considering boosters or under 12’s, Hankins said. “So, how do we get there?”
“Once we have everyone vaccinated there is a thought that we should definitely make sure we contribute to the world vaccination effort.”
Tania Watts University of Toronto