How bad is the measles threat in Ontario? Health officials aren’t sure

Amid the largest measles outbreak in 30 years, health officials in Ontario are “flying a bit blind”, a leading immunization expert is warning.

As cases of the highly infectious disease climb in Ontario and across the U.S., health officials are relying on an outdated system to understand vaccination gaps and to gauge the risk of further measles outbreaks across the province.

“We are a bit in the dark. It is hard to know how worried we should be,” said Dr. Kumanan Wilson, CEO and Chief Scientific Officer at Bruyère Health Research Institute. Wilson is also the co-founder of a technology company that created the CANImmunize app to help people track immunization, something that is used in Ottawa. He is among experts who have long called for an up-to-date immunization registry in Ontario to provide accurate, real-time data that can improve vaccination coverage and surveillance.

And he is not alone in worrying that it is difficult to get an accurate count of measles coverage in the province at a critical time.

From Jan. 1 until Feb. 27 in Ontario this year, there were 119 confirmed and 23 probable cases of measles, making it the worst outbreak in the province since the highly contagious disease was considered eliminated in Canada in 1998. Numbers continue to climb. This week, nine cases were confirmed in Hastings County, north of Kingston, confirming the outbreak has spread beyond southern Ontario. The vast majority of cases involve people who had not been immunized.

So far, there have been no recent cases in Ottawa. The last reported case of measles in Ottawa was in 2019, but officials around Ontario are watching case numbers elsewhere closely.

Last year, a child under five died of measles in Hamilton, the first death in the province since record-keeping began in 1989. A child has also died of measles in the United States this year.

Those cases coincide with waning vaccine coverage.

Public Health Ontario (PHO) recently published numbers from 2023-24 showing that an estimated 70 per cent of Ontario seven year olds were fully immunized against measles that year, well below levels needed to prevent outbreaks. In the 2019-20 school year, that number was 86.1 per cent. Ottawa’s numbers, according to the PHO data, were even lower — an estimated 64 per cent of seven year olds in Ottawa were fully vaccinated during the same year, compared to 81 per cent just a year earlier.

Most people in Ontario continue to use yellow booklets to keep track of routine childhood vaccines for illnesses such as measles. Parents and guardians are responsible for reporting their children’s immunizations to the local public health agency, something required by law. But, when there are gaps, it is a painstaking process for public health officials to determine whether those children are under-vaccinated or under-reported. Even then, the data is not timely.

Ottawa Public Health is undergoing school-based surveillance and has mailed 11,000 notices to students born in 2007 and 2017 that their vaccinations are not up to date. Suspensions could follow. But the risk from measles is difficult to accurately predict, in part because of the lack of an integrated vaccine registry in Ontario, Interim Medical Officer of Health Dr. Trevor Arnason said in a statement.

“We continue to face the difficulty of not having real-time information about measles immunization rates in Ottawa because there is no integrated registry in the province that would enable reporting by providers at the time the vaccine is given,” Arnason wrote. “Although the exact risk is difficult to determine, the cases throughout Southern Ontario are a reminder of the importance of routine vaccinations.”

That is one reason why sending notices through the school (under the Immunization of School Pupils Act) and follow-up are important and provide the “best estimates” of vaccine coverage.

Arnason noted that measles coverage rates among seven-year-olds in Ottawa were 64 per cent at the end of the 2023-24 school year and 90 per cent among 17-year-olds, but those were likely underestimates.

Measles is among the most contagious infectious diseases known to mankind. One person can infect as many as 18 others and the virus can remain in the air hours after an infected person leaves a room. In Canada, the national target is 95 per cent immunization coverage to prevent outbreaks.

While it seems clear many or most parts of the province are not meeting immunization targets, it is unclear how big the gap is. That is why Wilson says it is hard to know how worried people should be about the ongoing outbreak in Ontario and significantly larger ones in the U.S.

Wilson believes vaccination coverage rates are likely significantly higher than those estimates suggest.

“Seventy per cent would put us at (similar levels) as African countries. I don’t believe that is the case.” He said the numbers likely represented underreporting. Still, there are numerous signs that routine immunizations have dropped in the years since the beginning of the COVID-19 pandemic and remain lower than pre-pandemic levels despite ongoing efforts in Ottawa and across Canada to help children and families catch up.

“The No. 1 thing we should be worried about is that we don’t know how worried we should be,” Wilson said.

That knowledge gap is critical at a time when measles outbreaks are becoming more common across North America and large numbers of Ontario residents do not have access to primary care, which is where most routine vaccines are administered. Misinformation about vaccines is also making it more difficult to increase waning immunization levels.

Last September, the Ontario Immunization Advisory Committee issued a paper calling for a 21st century immunization registry in the province, saying it would help reduce the burden of diseases that vaccines could prevent, make it easier for people to get vaccinated, improve the delivery of Ontario’s immunization programs and ensure better use of health resources. It noted that just such a system was created during the pandemic for COVID-19 vaccines that allowed officials to closely monitor vaccine uptake in real time and to monitor for safety issues.

“Immunization registries are essential for maximizing the benefits of vaccines in the 21st century,” members of the advisory committee wrote. “An immunization registry would provide more efficient and accessible health care for people in Ontario and protect them from vaccine-preventable diseases, improve efficiencies within Ontario’s health system, and allow for comprehensive program monitoring and evaluation of vaccine uptake, safety and effectiveness.”

A spokesperson for the Ministry of Health said the Ontario government “continues to work with our partners to make it easier and faster for Ontarians to securely access their health information when and where they need it.” Spokesperson W.D. Lighthall noted there was a central database, Panorama, used by public health units to record routine vaccinations. That information, generally, has to be provided by individual parents. He didn’t directly respond to a question about the recommendation for a real-time immunization registry.

Wilson says Ontario would benefit from a vaccination registry system that would work like some of Ontario’s screening programs to not only keep an accurate, timely record of people’s vaccinations, but also send out reminders when they are out-of-date. He suggested that might be done through the currently existing BORN (Better Outcomes Registry and Network) Ontario, which is based at CHEO and collects and manages data about pregnancy, birth and childhood in Ontario. It already has the structure and legal framework needed for such work, Wilson said.

“In an ideal world, we would have real-time collection and even before an outbreak, you can go to a neighbourhood and start to notify people right away who have not been vaccinated,” Wilson said.

Our website is your destination for up-to-the-minute news, so make sure to bookmark our homepage and sign up for our newsletters so we can keep you informed.