Measles is surging in Alberta. Which vaccine-preventable disease could be next?

Doctors and scientists worry Alberta's measles outbreaks could signal the start of a new era when other dangerous infectious diseases of the past could re-emerge and pose new health threats.

The province is battling its worst wave of measles cases in nearly half a century and there is no end in sight.

The virus was declared eliminated in Canada in 1998. But vaccination rates have declined in Alberta, and around the country in recent years.

"To some extent measles is the canary in the coalmine," said Dr. Cora Constantinescu, a pediatric infectious diseases specialist at Alberta Children's Hospital in Calgary.

As of Friday, a total of 879 measles cases had been reported in the province since the outbreaks began in March.

"When the immunization rates go down and you have a lot of unprotected people in the communities, usually the first vaccine-preventable disease to come back is measles," said Constantinescu on a measles episode of CBC Radio's Alberta at Noon.

It's one of the first to re-emerge, experts say, because it is so highly contagious and requires very high vaccination rates (about 95 per cent) for population level protection.

Provincial data shows in 2024 just 68.1 per cent of Alberta two-year-olds were up to date with two doses of the measles vaccine.

The level of immunization needed for herd immunity varies from one disease to another, but vaccination rates for other childhood illnesses are dropping too, sparking fears about what's next.

"For many diseases we have now fallen, again, below herd immunity," said Craig Jenne, a professor in the department of microbiology, immunology and infectious diseases at the University of Calgary.

"We're getting into the realm where diseases that were really problematic here in Canada in the 1950s and 60s — and that through a really comprehensive and well-co-ordinated vaccination campaign were largely eliminated — are coming back."

• Alberta's measles outbreaks are now the worst in nearly half a century

It's a big concern for University of Alberta infectious diseases specialist Dr. Lynora Saxinger as well.

"To me it's a little bit of a red flag in terms of what we might be seeing of other diseases of the past. Maybe it won't be so much in the past anymore," she said.

"And that is a large burden of illness that can have complications in a lot of different ways."

These diseases, while often forgotten, can be life-changing and even deadly.

"We worry about seeing resurgence of things like polio, that we really have not had for a long time," said Dr. Stephanie Smith, an infectious diseases specialist at the University of Alberta Hospital.

Polio is highly infectious and can infect the nervous system. While many people have mild flu-like symptoms, or no symptoms at all, they can still spread the illness.

And in some cases it can lead to paralysis and even death.

"We've all seen the historic pictures of people in iron lungs to support breathing. There's no reason why that couldn't happen again if we see polio re-establish in the province," said Jenne.

Polio outbreaks spread unfettered across the country for decades.

In 1953 — a particularly bad year for the virus — there were 9,000 cases and 500 deaths reported.

According to the Public Health Agency of Canada (PHAC) widespread immunization led to a dramatic drop in polio cases in the 1950s. The last time wild poliovirus was acquired in Canada was 1977 and the country was declared free of the wild poliovirus in 1994.

Alberta's routine childhood immunization schedule recommends babies receive doses of the vaccine that protects against polio (IPV) at two months of age, four months, six months and 18 months. An additional dose is offered at the age of four.

The injections also protect against diptheria, tetanus, and pertussis (DTaP).

Provincial data shows 75.8 per cent of two-year-olds were up to date with four doses of the vaccine in 2015.

That number dropped to 68.9 per cent in 2024.

According to Jenne, polio vaccine uptake needs to be at least 80 to 86 per cent for herd immunity.

In 2024, the north, central and south zones had the lowest rates, hovering between 55 and 56 per cent.

In some localized areas the uptake is extremely low.

In High Level, for example, 13.4 per cent of two-year-olds had four doses of the polio vaccine in 2024. Two Hills County reported 17.3 per cent and the Municipal District of Taber reported 28.7 per cent.

"[With] polio and all sorts of other vaccine-preventable illnesses, it's concerning that we see vaccination rates being low for all of those," said Smith.

Pertussis, which is also known as whooping cough, has already flared up in Alberta.

"Whooping cough is very dangerous for infants under the age of one," said Jenne.

Pertussis can lead to serious complications in young babies including pneumonia, seizures and death.

Vaccination rates for it have fallen alongside polio.

"One to four deaths related to pertussis occur each year in Canada, typically in infants who are too young to be immunized, or children who are unimmunized or only partially immunized," the PHAC website states.

There were 894 confirmed cases of pertussis in Alberta in 2023, when outbreaks were declared in all health zones. And outbreaks have since continued.

"It is a changing landscape now where unfortunately the advantage is tipping in favour of these infectious diseases," said Jenne.

Doctors worry about mumps and chicken pox as well.

Saxinger said Alberta's overall vaccination rates tend to be lower than many other jurisdictions and she wants people to know these are not just benign childhood illnesses.

"There is genuinely a lot of concern around the whole vaccine-preventable disease front," she said.

"We're not thinking about people who had complications along the way and the burden of that in a community."

And as doctors and scientists watch Alberta's measles case counts balloon, that sense of urgency grows.

"We have tools to bring them back under control. It just requires significant effort — significant co-ordination — and we need the public to step up and get those vaccine rates back up to the protection that we had enjoyed for the last two or three decades that really saw these diseases eradicated from Canada," said Jenne.