WATCH ABOVE: Officials are warning people about a measles outbreak in the GTA. Laura Zilke reports.

TORONTO — Jennifer Webster made sure her two children were vaccinated according to schedule. But among parents at her Toronto school, she’s in the minority.

“My kids were born early — they were preemies and vaccination was part of helping them stay healthy,” Webster told Global News.

The Toronto mom sends her kids to Alpha Alternative School, where kids aren’t graded, aren’t handed homework and are exempt from provincial testing.

At the small, unconventional school in downtown Toronto, vaccination rates for MMR — measles, mumps and rubella— and DPT — diphtheria, polio and tetanus — sat at 43.75 and 45 per cent, respectively in the 2011-12 school year, according to health information collected by the city.

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According to those numbers, the school had the lowest vaccination rate in the city that year.

READ MORE: Anti-vaccination movement means preventable diseases are making a comeback

Toronto Public Health vaccination rates for every school in Toronto – obtained exclusively by Global News under the Freedom of Information Act – suggests a significant disparity in vaccination uptake across the city. But many schools are well below the herd immunity rate of 95 per cent – the level at which, according to the Public Health Agency of Canada, there are enough people immunized to protect everyone.

“It’s an issue and we’ve been struggling with it,” said Dr. Barbara Yaffe, associate medical officer of health and director of the communicable diseases program at Toronto Public Health.

“It troubles us because we want everybody to be immunized and protected as best as possible.”

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Interactive: Explore the map to see which Toronto schools are above and below the 95% herd immunity level for measles vaccination rates. Enter an address or postal code in the search box, double-click to zoom and click and drag to move around. Click a school for details.

Measles, mumps, rubella vaccination rates for Toronto schools, 2012 » Measles, mumps, rubella vaccination rates for Toronto schools, 2012

Toronto Public Health assesses immunization records for every student in each Toronto school. If students are not up to date with vaccines, they must provide a notarized exemption based on medical, religious or philosophical reasons.

Students who don’t provide vaccination documentation or an exemption are sent home with Toronto Public Health warnings. On the third warning, they’re suspended from school for up to 20 days.

During the 2011-12 school year, just over 3,000 students were suspended across the city. Most students returned to school within one day to two weeks once they provided proof of their immunization. Fewer than two per cent returned with an exemption post-suspension.

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The national measles, mumps, rubella vaccine uptake in Canada is about 95 per cent, according to the Public Health Agency of Canada.

READ MORE: Should flu shots be mandatory for health care workers?

Herd immunity varies by disease; for measles, it should be at about 95 per cent uptake for the two doses, said Dr. John Spika, director general of the public health agency’s centre for immunization and respiratory infectious diseases.

He doesn’t believe there is a growing anti-vaccination “movement” per se. In Canada, only one per cent of Canadians sampled refused immunization. Another four per cent hasn’t immunized their kids according to schedule.

“But [those numbers] haven’t really grown from what we can tell,” Spika told Global News. The federal agency has been tracking immunization coverage since the 1990s.

As for Toronto’s vaccination rates, Spika isn’t necessarily worried.

“That’s troubling to me if you were telling me it was for all of Toronto,” he said.

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For the most part, Toronto students are vaccinated, Yaffe said. It’s just that they don’t have the proof on hand. Sometimes, students are coming from another country and immunization records could be in a different language and need to be translated. In other instances, families need to track down archived medical records from their doctors.

Meanwhile, students switch schools during the year and that can skew a school’s vaccination rate. According to the Ontario schedule, the MMR booster vaccine is doled out between the four to six-year-old mark — once kids turn seven, they’re automatically supposed to present proof that they’ve been vaccinated.

Data is constantly fluctuating, Yaffe said. The numbers in September are typically higher, but by June, because of these factors, the vaccination rates may look like they drop off.

READ MORE: Vaccination – all natural but without the illness

“Those are really some of the factors that play into the lower coverage rate than you would like and those are really a symptom of the information system,” Yaffe said.

The database — called IRIS or Immunization Records Information System — is outdated, Yaffe said. If a parent vaccinates his or her child, the onus is on them to get the proof from the doctor and hand it to health officials. There has to be a more seamless way, Yaffe said.

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Medical exemptions are typically rare. Doctors forgo vaccinations if their patients have already had the disease, there’s evidence the child is already immune or they have allergic reactions.

Philosophical or religious reasons are even more of an anomaly, making up at most 1.5 per cent of the school population, Yaffe said.

“There will be pockets of parents who tend to be highly educated, who have read a lot of information on the Internet and are very concerned about the safety of the vaccine so there will be a very small number of schools that have parents like that,” Yaffe said.

Jodie Peacock, a Oakville mother, hasn’t vaccinated any of her three kids. She doesn’t plan to until they’re at least four years old.

“We know that at the age of two months, the immune system is so immature that giving a vaccine for five different conditions all in one shot from an immunology point of view really doesn’t make a lot of sense,” the naturopath told Global News. Physicians have rejected that theory, saying vaccine schedules exist to maximize the benefit to a child’s immunity.

“It’s not a natural way to be exposed to something,” she said. To her, the chicken pox vaccine isn’t necessary — most kids catch the chicken pox and survive. She says she feels the same way about measles.

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“It’s looking at each individual vaccination, what your risk is of potentially contracting it and what are the consequences,” Peacock said.

READ MORE: What caused a whooping cough epidemic? Scientists blame parents

But measles, mumps, chicken pox and whooping cough are highly contagious and potentially fatal. Along with measles outbreaks, whooping cough, chicken pox and mumps — all preventable with vaccines — have resurfaced in the Western world.

Put your son or daughter in the same room as a child with chicken pox, and he or she will probably be infected within five minutes.

University of Toronto scientists say that if vaccination rates dropped by 10 per cent, the city could see large outbreaks of measles — as many as 50,000 cases in less than five years.

Watch: Dr. Jennifer Gardy, senior scientist for the B.C. Centre for Disease Control, explains how diseases previously believed to have been eliminated – like Measles – are making a comeback.

Right now, about 228 cases of measles have popped up in B.C. Handfuls of cases have been reported in Manitoba and Alberta.

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Toronto has seen six cases of measles in 2013. Over the weekend, a Halton region hospital said another case surfaced. So far, a single has been confirmed in Toronto this year.

A single case of measles in Toronto is considered a potential outbreak. If a Toronto student catches the measles, for example, any of his or her unvaccinated classmates are sent home. Sometimes that’s enough to push parents into vaccinating their child so he or she can get back into the classroom, Yaffe said.

Dr. Marc Ouellette, scientific director of infection and immunity at the Canadian Institutes for Health Research, said Toronto’s vaccination rates leave him “worried.”

“We’d have to look at the socioeconomic and cultural landscape of those specific schools [in the lower half],” Ouellette said.

CIHR is launching funding to study immunization and vaccine uptake.

“We have to further understand the motivation that brings parents against vaccines, and for that we’ll need more research.”

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carmen.chai@globalnews.ca

Follow @Carmen_Chai