Why are measles case counts climbing so high in Alberta? Experts weigh in

CBC

12-05-2025

Infectious disease experts are raising the alarm about measles spread in Alberta, warning case counts are far higher than neighbouring provinces and they're increasing rapidly.
Alberta reported 116 more measles cases last week, pushing Alberta's total of confirmed cases to 326 as of Friday.
"[It's] really the largest growth in the number of cases of measles — at least per capita — of any place in Canada," said Craig Jenne, professor of microbiology, immunology and infectious diseases at the University of Calgary.
"It's going to be very difficult to rein this in."
Alberta's case counts are second only to Ontario, which has reported more than 1,400 cases since its outbreaks began in October.
That province, which has three times the population, recorded 197 new cases in its latest weekly update.
Neighbouring provinces are not nearly as hard hit.
As of Friday, British Columbia had reported eight cases and Saskatchewan's tally sat at 27.
"We are almost at a tipping point where either we bring everything to the table and put some resources into trying to contain this or we might see numbers going up towards what we are seeing in Ontario," said Dr. Lynora Saxinger, an infectious diseases specialist at the University of Alberta.
Alberta's south zone is the hardest hit with 200 cases as of Friday. The central zone had reported 86 cases by the end of the week.
Why is Alberta so hard hit?
"The single most predominant determinant of whether measles spreads is vaccine status," said Jenne.
"Alberta is typically below most other jurisdictions. And there are regions of Alberta that are significantly below the other provinces, and these really provide the tinder for these growing fires of infectious disease."
According to the Alberta government website, two doses of the measles vaccine offers nearly 100 per cent protection.
Provincial data shows 71.6 per cent of seven-year-olds were up-to-date with both doses of the vaccine in 2024.
That's far below the 95 per cent threshold experts say is needed for population-level protection.
Next door in Saskatchewan, vaccination rates are higher.
According to the Saskatchewan Ministry of Health, 87.4 per cent of seven-year-olds in that province were fully vaccinated with two doses of the measles vaccine in 2024.
Meanwhile, data from British Columbia shows 72.4 per cent of children who turned seven in 2022 were up-to-date with two doses.
To understand why outbreaks are growing the way they are, it's important to look at vaccination rates in localized areas where cases are occurring, according to Saxinger.
She said there's been transmission in some small, close-knit communities with really low vaccination rates, which also happened in Ontario.
"If you imagine a fire shooting off sparks, then where it lands — if there's tinder nearby or not — really determines what's going to happen," Saxinger said.
If a measles case ends up in a social group where few people get immunized, cases will spread quickly.
Provincial data shows that in Two Hills County, only 24 per cent of seven-year-olds were fully vaccinated with two doses in 2024. It's been one of Alberta's hot spots for cases.
Other regions with very low vaccination rates include High Level (30.6 per cent), the County of Forty Mile (30.2 per cent) and the Municipal District of Taber (39.1 per cent).
"Average numbers tend to under-represent areas in the province that might be significantly below the reported provincial areas, and it's those areas that really are the hot spots," said Jenne.
Urban areas tend to have higher rates than rural parts of the province, he noted.
In Ontario, immunization rates have also dropped over the past decade.
That province's most recent data shows that 70.4 per cent of seven-year-olds were up-to-date with their measles vaccine in 2023-24. Immunization rates were as low as 24.6 per cent in the Halton region.
How quickly a province responds and increases vaccination rates can also impact the severity of a measles outbreak, according to Saxinger.
The speed of contact tracing, whether or not contacts agree to quarantine after exposure and whether or not they'll take post-exposure prophylaxis, are also factors, she said.
"Those things make a big difference. And I think Ontario's had struggles in all of those. And we might be facing a similar situation."
Delay concerns
Measles is highly contagious and can lead to severe complications, including pneumonia, brain swelling and even death.
Dr. James Talbot, a former chief medical officer of health for Alberta, calls the situation "concerning," noting there are more cases in the community than the numbers reflect.
That's because there is a lag time between when people are exposed to the virus and when they develop symptoms, get tested and then have confirmation through lab testing.
"The way infectious diseases work is exponentially," said Talbot during a media availability hosted by the Alberta Medical Association on Thursday.
Once Alberta reaches a thousand cases, he explained, statistics show you can expect between one and three deaths.
"We don't want to be in that situation," he said. "Our concern is that we had an opportunity to make a difference earlier on. We're in a situation now where those opportunities have passed and we're starting to see a significant increase in the disease."
Following weeks of calls by health experts for a stronger response, the provincial government announced plans last week to improve immunization accessibility and launch an ad campaign promoting vaccination.
But any bump in immunization rates resulting from those changes will take time to have an impact, he said.
According to Talbot, once a person decides to get vaccinated and gets an appointment, it takes between seven and 14 days for immunity to take hold.
"Not only are we behind the curve in terms of the numbers that are being reported out, we're potentially behind the curve in being able to respond and getting people as protected as possible."
In a statement emailed to CBC News, an Alberta Health official acknowledged the measles outbreaks are having an impact on individuals, families and communities around the province.
We continue to monitor the situation closely. Public health officials are doing an excellent job working with impacted communities, responding swiftly, and ensuring that appropriate measures are in place to help limit further spread," the spokesperson said.
"Immunization remains our best defence, and we strongly encourage all Albertans to ensure their vaccinations are up-to-date."
The province said some of its awareness campaign has already launched on social media and through online digital advertising.
And print ads, with a focus on rural communities in central and south zones, as well as provincewide radio ads, are expected to launch this week.
Alberta's early childhood immunization schedule recommends a first vaccine dose at 12 months and a second at 18 months.
The province is offering babies as young as six months of age an early and extra dose if they live in or are travelling to the south, central or north zones.