Why reports of COVID-19 infections after 2 vaccine doses aren't cause for alarm
'Breakthrough infections' among fully vaccinated Canadians just 0.5 per cent of reported cases, data shows
At first glance, reports of people getting infected with COVID-19 despite being fully vaccinated can sound alarming, as if this crop of long-awaited vaccines aren't doing their job.
A Toronto hospital recently announced an outbreak involving cases among people who'd received one or both vaccine doses.
Back in May, nine cases of COVID-19 were reported in just one week among fully-vaccinated members of the New York Yankees baseball team and its staff.
And across Canada, deaths from the illness have even been reported among individuals who've had two shots, including a senior in Manitoba in May and an elderly long-term care resident in Ontario a month later.
But there are two key things to keep in mind about these "breakthrough infections." For one thing, they're rare — making up around 0.5 per cent of reported COVID-19 cases since vaccination efforts began, the latest Canadian data shows.
And when post-vaccination infections do happen, they typically tend to be mild.
- Have a question or something to say? CBC News is live in the comments now.
Experts also stress that while no vaccine offers perfect protection for every single person, the relatively infrequent examples of serious infections after full vaccination — coupled with the dramatic drop in cases, hospitalizations, and deaths from COVID-19 — show these vaccines are indeed doing their job, and excelling at it.
"Ultimately, what we want the vaccine to do is prevent people from getting severely ill," explained immunologist and researcher Matthew Miller, an associate professor at McMaster University.
Even in cases where breakthrough infections do occur, he continued, those infections tend to be a lot less severe than cases reported in partially vaccinated or totally unprotected individuals.
"Anybody can tolerate a runny nose for a few days," Miller said. "What we really want to ensure is that people aren't ending up in the hospital, on ventilators, fighting for their lives."
Few Canadians dying of COVID-19 post-vaccination
So far, close to 34 million vaccine doses have been administered in Canada, and reports of breakthrough infections after full vaccination remain low.
The latest Public Health Agency of Canada (PHAC) data, provided in response to questions from CBC News, shows 2,731 cases of COVID-19 among fully vaccinated individuals have been reported in Canada's national data set as of June 21.
Someone is fully vaccinated two weeks after their second vaccine dose, reflecting the minimum time period needed to build full immunity, according to PHAC.
The data shows infections among fully vaccinated Canadians represent just 0.5 per cent of the COVID-19 cases reported since the country's vaccine rollout started in December.
That finding reflects data from 10 provinces and territories which currently report vaccination information to federal public health officials. It doesn't include figures from Quebec, Saskatchewan, or Newfoundland and Labrador.
In a statement, PHAC spokesperson Tammy Jarbeau noted that people who got COVID-19 following vaccination — either partial or full — were less likely to die than unvaccinated individuals. The "protective effect was significant" among partially vaccinated people over 60 and fully vaccinated people over 80, Jarbeau added.
Only 0.0027 per cent died from due to COVID-19 while partially vaccinated and 0.0018 per cent died while fully vaccinated, according to PHAC.
It's a similar scene in the U.S., where more than 319 million doses have been doled out to date.
A recent Associated Press analysis found nearly all recent COVID-19 deaths in the U.S. — now down below 300 per day on average — are in people who weren't vaccinated.
The findings, based on government data from May onward, showed that breakthrough infections in fully vaccinated Americans accounted for fewer than 1,200 of more than 853,000 COVID-19 hospitalizations, or about 0.1 per cent.
As for deaths, only around 150 of the more than 18,000 COVID-19 deaths in May were in fully vaccinated people, which equals around 0.8 per cent of the total recent death toll.
WATCH | Deaths, hospitalizations drop among elderly as COVID-19 vaccinations ramp up:
Milder cases more likely post-vaccination
Despite the relative rarity, dire-sounding reports of post-vaccination outbreaks tend to make headlines.
In situations like hospital outbreaks or cases on sports teams — or any other setting where people are getting tested regularly — it's easier to catch under-the-radar infections where people might not even feel ill, noted Dr. Sumon Chakrabarti, an infectious diseases specialist with Trillium Health Partners in Mississauga, Ont.
"People are reading that as, 'Oh, they got COVID and had the vaccine,'" he said. "But health-care workers are looking at that as people who tested positive but weren't symptomatic."
When it comes to both the recent Toronto hospital outbreak and the New York Yankees cases, the infections among vaccinated individuals were mild — most Yankees staffers who wound up testing positive for the coronavirus didn't show symptoms at all.
The fact that most breakthrough cases aren't serious means those individuals don't put strain on the health-care system, which can have a worrisome ripple effect on hospitals' ability to conduct other non-COVID appointments and procedures, as Canada experienced throughout much of the pandemic, Chakrabarti noted.
"What worries us is not people who are getting COVID and having minimal symptoms," he said. "What worries us is people who are getting really sick and requiring hospitalization, and oxygen, and mechanical ventilation."
WATCH | Shifting COVID-19 symptoms could change how virus is tracked:
For some people, vaccines don't work
As vaccination efforts ramped up this year, fewer older, fully-vaccinated Canadians experienced dire outcomes from COVID-19, CBC News previously reported.
But even while population-level protection ramps up, some vaccinated individuals could still wind up seriously sick.
Miller said that's not because the vaccines aren't working well, but rather someone's immune system might be sluggish. That could be due to factors like a genetic condition or medication someone is taking, he explained.
"You're talking about, globally, billions of vaccine doses — there will be individuals for whom the vaccine basically hasn't worked," Miller said. "And as a result of that, we see a breakthrough."
Another high-profile hospital outbreak in Calgary, for instance, involved 23 cases of the more-transmissible delta variant among patients and staff, and nearly half of those infected were fully vaccinated.
Two people who got COVID-19 died, including one patient who was unvaccinated and another who'd had both doses — but in each case the individuals had significant underlying health conditions.
Experts who previously spoke to CBC News speculated the outbreak may also have been worse without such high levels of vaccination.
WATCH | Immunologist explains how "breakthrough infections" can happen:
Concerns over hesitancy
Despite the rarity of breakthrough infections, medical experts are concerned reports of post-vaccination cases and deaths could fuel hesitancy among Canadians still waiting to get their shots.
Chakrabarti said it makes sense if some people are alarmed after living through such a "traumatic year." But what's key, he said, is for officials to provide clarity that these vaccines are indeed working as advertised.
"What we need is very good, strong public health messaging, with a shift in our perspective now," he added. "We are not in the same place we were in March 2020."
Primary care physicians, town halls, and door-to-door community ambassadors are crucial for reaching vulnerable, marginalized — and often racialized — communities, where people are already wary of Canada's vaccination push, noted Akwatu Khenti, an assistant professor at the University of Toronto's Dalla Lana School of Public Health and the chair of the Black Scientists' Task Force on Vaccine Equity.
"We just have to try as much as possible, to move as fast as possible, with the vaccine rollouts for those low vaccine-coverage communities," he said.
And getting shots in arms means simplifying the messaging about vaccine effectiveness and breakthrough infections, Khenti explained.
"No one ever argued that the COVID vaccination will protect you 100 per cent," he said. "But what it does protect you from, to a significant degree — which can't be argued against — is hospitalization and death."
Have a coronavirus question or news tip for CBC News? Email: Covid@cbc.ca or join us live in the comments now.
ABOUT THE AUTHOR
