Canada eliminated measles in 1998. But measles has come back with a vengeance.
The World Health Organization (WHO) reported a 79% spike in the number of documented global measles cases in 2023 from 2022.
By the end of 2024, more than half of all the countries in the world will be at high or highest risk of measles outbreaks unless urgent preventive action is taken, WHO predicts.
Global resurgence gaining momentum in Canada
What does the global resurgence of measles mean for the health of Canadians and what should we do to prepare and protect against a potential tsunami of cases here?
鈥淭he United States and countries across Europe had significant measles outbreaks last year. It鈥檚 almost inevitable that we will see some large outbreaks in Canada,鈥� says Dr. Brian Ward (MCDM鈥�80, PGME鈥�92), professor in the departments of Medicine (Division of Experimental Medicine) and Microbiology and Immunology, and senior scientist at the Research Institute of the 不良研究所 Health Centre. 鈥淲e should be worried and start taking appropriate precautions to ensure that Canadians who are unvaccinated or under-vaccinated against measles are protected. Measles is almost 100% preventable with two doses of the MMR [measles, mumps, and rubella] vaccine.鈥�
The worldwide measles resurgence has already reached Canada and is gaining momentum. There were only three measles cases here in 2022 and 12 cases in 2023. But Quebec alone had 51 confirmed cases by the third week of May; Ontario had 22 cases, including the death of an unvaccinated child under five from Hamilton, and cases have been reported in British Columbia, Alberta, Saskatchewan and Manitoba.
While the case numbers in Canada may seem relatively small, measles can spread like wildfire when vaccination rates fall well below the target rate of 95% coverage for children. Canadian modelling studies suggest, for example, that a measles outbreak in an 8,000-person community with only 55% vaccine coverage could result in nearly 3,000 cases. In some Montreal schools, measles vaccine uptake had plunged below 50, 40 or even 30 per cent by early this year. The emerging measles threat spurred the province of Quebec to launch pop-up MMR vaccination clinics in multiple Montreal hospitals and schools in March to halt transmission and prevent further spread of the disease.
Time to shed complacency
Until this year, Canada had been insulated for decades from an old, highly contagious infectious disease that can cause pneumonia, encephalitis (brain inflammation and swelling), blindness, deafness, permanent neurological consequences and even death.
鈥淢easles is a severe disease that many Canadians have forgotten about because they鈥檝e been successfully protected by the vaccine. Yet, it鈥檚 much more transmissible than SARS-CoV-2 and the influenza virus,鈥� says Ward, noting that the modern MMR vaccine was introduced in Canada in 1971.
鈥淚t鈥檚 a very nasty virus and prior to HIV, measles was the most immunocompromising infectious disease we knew of. Measles infects immune cells, a bit like HIV, and a patient鈥檚 immune system isn鈥檛 the same after being infected. The youngest children are at highest risk of dying due to complicating super-infections such as pneumonia or severe diarrhea,鈥� explains Ward, a longtime measles researcher, who first conducted measles field studies in Peru as a research fellow at Johns Hopkins University School of Medicine in the late 1980s.
Internationally, however, the measles resurgence began several years before the COVID-19 pandemic. It was fuelled by stagnant, inadequate vaccination rates and massive outbreaks in countries such as the Democratic Republic of the Congo, which had 250,000 measles cases and over 5,000 deaths in 2019. 鈥淕lobally, there was a downward trend in measles cases from 2000 to 2016-2017. 2018 was a watershed year when that trend was reversed, and cases started going up each year,鈥� observes Ward. 鈥淐ases are now rising rapidly in high-, middle- and low-income countries due to several factors, including conflicts, disruption by COVID-19 of vaccination programs, and growing vaccine resistance in many communities.鈥�
Overcoming the vaccine hesitancy hurdle
Just as winning over undecided voters can turn the tide in an election, persuading Canadians who are hesitant to vaccinate their children鈥攐r themselves for international travel鈥攊s key to protecting their own families, preventing local outbreaks, and stopping or reversing the spread of the disease in Canada.
鈥淢easles is a horrible disease that people often don鈥檛 take seriously enough,鈥� says Dr. Srinivas Murthy (MCDM鈥�06), a pediatric intensive care physician at BC Children鈥檚 Hospital and a clinical associate professor in the Department of Pediatrics, Faculty of Medicine, University of British Columbia. 鈥淓ducating parents about the potentially serious complications of measles could help boost vaccination rates. Without knowledge and details about the disease and the vaccine鈥檚 effectiveness, people tend to be more skeptical. Fear about what could happen is one of the strategies that may persuade some parents who are hesitant to vaccinate their children.鈥�
Another incentive for hesitant parents to vaccinate their kids is that unvaccinated students would be excluded from school during a measles outbreak. 鈥淪chool health districts and school boards should collaborate to organize vaccination catch-up programs in areas where measles vaccination rates are low,鈥� says Ward. 鈥淎s we start to report outbreaks in Canada, I hope more vaccine-hesitant parents will be motivated to vaccinate their children. If a family has three unvaccinated kids and there is an outbreak in their school, their children could be at home for a month or two.鈥�
For adults planning to travel internationally, the Public Health Agency of Canada recommends that those born in 1970 or later get two MMR doses and adults born before 1970 get at least one dose. 鈥淭here is no downside to giving people an extra dose of measles vaccine,鈥� advises Ward.
Tailoring vaccine campaigns to community needs
In the spring of 2021, Tammy Bui (MSc鈥�21) and Nehal Islam (MSc鈥�21, MCDM鈥�25) co-founded WeCanVax as a student initiative to combat COVID-19 vaccine hesitancy in historically underserved or racialized communities. Bui had designed a broad social media campaign for her Foundations of Health Promotion course and WeCanVax received a $10,000 Vaccine Innovation grant from the Public Health Agency of Canada to help boost vaccination rates in Parc-Extension, a vibrant and multicultural borough in Montreal where two out of three residents are immigrants or refugees.
鈥淲e presented our idea to community leaders, and they advised that a generic social media campaign wouldn鈥檛 work because some residents didn鈥檛 have access to a smartphone or stable internet. We had to rethink our approach to co-create and co-design a tailored campaign that met the community鈥檚 specific needs,鈥� says Bui, a Class of 2023 Schwarzman Scholar, now working as an epidemiologist in policy and international engagement at the Public Health Agency of Canada. 鈥淚 understand those needs because my parents were Vietnamese refugees who had to struggle with similar language, transportation and socioeconomic barriers.鈥�
Based on feedback from residents, Bui and Islam created posters featuring photographs of various community members who had been vaccinated and testimonials in multiple languages about why they wanted to be vaccinated. 鈥淎 lot of the people featured in the posters reported that other community members asked them questions about the vaccine and how they could get it. This had a snowball effect,鈥� says Islam, whose parents were refugees from Bangladesh. 鈥淏y August 2021, Parc-Extension鈥檚 vaccination rate exceeded the Montreal average by 10% due to the combined efforts of various tailored initiatives including our own.鈥�
Bui believes that many of the lessons learned by WeCanVax to effectively promote COVID-19 vaccine confidence could help boost vaccine uptake for measles. 鈥淚t鈥檚 very important to understand the reasons why people in a particular community haven鈥檛 been vaccinated. We learned early on the reasons people in Parc-Extension didn鈥檛 get vaccinated were based on barriers such as language, culture, socioeconomics, and transportation,鈥� she says. 鈥淭hese reasons would be very different in another borough such as Ville-Marie.鈥�
Making measles or COVID-19 vaccination convenient and accessible is extremely important for people who can鈥檛 afford to take time off work, who do shift work, or who don鈥檛 have a car. 鈥淲e promoted after-school vaccination programs and set up mobile vaccination clinics in parks so parents and their kids could get their shots while walking through or playing in the park. A community-led grassroots approach that addresses the specific needs and barriers faced by the local population and builds trust with community residents can be applied to vaccine promotion for any serious infectious disease, including measles,鈥� says Bui.