Conflicting data from around the world creates divide over who should get boosters
Adam Miller
[Excerpt] Emerging research from around the world has sparked new fears about the declining protection COVID-19 vaccines provide over time against infection from the highly contagious delta variant, prompting some countries to move aggressively toward booster shots.
But the research these decisions are based on isn’t definitive, and CBC News spoke to several Canadian and international experts who raised concerns with the controversial move to roll out third doses widely before more data is available and while much of the world remains unvaccinated.
“We’re planning to hand out extra life-jackets to people who already have life-jackets, while we’re leaving other people to drown without a single life-jacket,” Dr. Mike Ryan, the World Health Organization’s top emergencies expert, said during a news conference Wednesday.
The WHO has recently called for a moratorium on boosters until at least the end of September. But despite the concerns raised by health officials and other experts, countries are forging ahead with plans for additional doses now — including parts of Canada.
Rapid shift to boosters worldwide
Israel extended booster shots to everyone over 40 on Friday, while France, Germany and the U.K. have announced third doses only for vulnerable populations at heightened risk of declining COVID-19 immunity.
The U.S. went a massive step further this week by announcing third doses for all Americans beginning next month, to bolster immunity against the much more contagious delta variant amid early signs the effectiveness of the vaccines could be dropping.
Several Canadian provinces have also made the decision to break away from the pack and pre-empt upcoming guidance from the National Advisory Committee on Immunization (NACI) on when booster shots may be needed and for whom.
Ontario will offer third doses to vulnerable populations, such as those in long-term care, First Nations elder care lodges and “higher risk” retirement homes, as well as for transplant recipients, certain cancer patients and other immunocompromised individuals.
Saskatchewan and Quebec previously announced plans to offer additional doses of mRNA vaccines — not because of waning immunity or the threat of delta, but for people who want to travel to countries that may not recognize mixed-vaccination status.
The tides have shifted rapidly on this issue over the past week and many Canadians may now be left wondering whether they’ll need an additional shot — and when they’ll get it.
Vaccine effectiveness data ‘all over the place’
What prompted the sudden shift in favour of widespread booster shots?
The answer is largely based on conflicting emerging data from highly vaccinated countries around the world that signal a potential drop in immune protection in the population over time amid surges in cases driven by the delta variant.
But the data is anything but clearcut.
“The vaccine effectiveness data that we’re getting are all over the place,” said Deepta Bhattacharya, an immunologist at the University of Arizona.
“It’s really hard to know what to make of all this, in part because all of these things are being estimated outside of the context of a clinical trial where you have a lot of control.… Now it’s a mess.”
In a country where delta is the dominant strain, Israel’s Ministry of Health released data late last month that implied two doses of the Pfizer-BioNTech vaccine was just 39 per cent effective against COVID-19 infection, a drop from 95 per cent seen in clinical trials and 64 per cent in real-world data earlier this year.
But experts have raised concerns about the quality of Israel’s data, suggesting it should be taken with caution before being used to justify the widespread use of boosters.
“Much of the Israel data can be explained by the fact that with delta waltzing onto the scene, those who have been vaccinated longest are also those more likely to experience severe illness than others — in other words, the elderly,” said Bill Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health.
“It is confusing because in some analyses, age is corrected for, but in others, not all.”
While it is reasonable to expect there is some waning protection from vaccines, especially with the spread of delta, Hanage said it’s not to the extent that’s being “bandied about” from the Israeli data and isn’t necessarily seen in younger age groups.
Dvir Aran, a biomedical data scientist at Technion — Israel Institute of Technology in Haifa, told CBC News he’s “very skeptical” about the Israel estimates.
“The vaccine effectiveness that was calculated by the Israeli Ministry of Health is from a mix of early and late vaccinated individuals,” he said, pointing to a lack of adjustment for confounders, or other factors, in the data. “So it’s not clear what it even means.”
Because of the different vaccines, rollout strategies and populations in each country, Hanage said it’s reasonable to suspect the Israel data is skewed — especially because one would expect to see the dramatic results replicated elsewhere.
“If you are relying on them as the grounds for a huge decision like boosters, that’s not as strong a foundation as you’d like.”
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