The Resurgence of Measles in Canada: A Cause for Concern
Measles, once nearly eradicated in Canada, is making a troubling comeback in 2025. As of February 21, 2025, the country has reported 95 measles cases, marking a sharp increase compared to the mere four cases reported during the same period last year. The majority of these cases are concentrated in British Columbia, Manitoba, Ontario, and Quebec. This trend is particularly alarming, as Canada had already recorded 146 measles cases by the end of 2024. Dr. Isaac Bogoch, an infectious diseases specialist at Toronto General Hospital, underscores the gravity of the situation, stating that the number of measles cases in Ontario by February 2025 is roughly the same as the total cases reported in all of 2024. This suggests that the country is not moving in the right direction in controlling the spread of measles.
The High Contagiousness of Measles
Measles is one of the most contagious infectious diseases, far surpassing the transmissibility of COVID-19, influenza, and chickenpox. Its high contagiousness is a key factor in the rapid spread of measles outbreaks, particularly in areas with low vaccination rates. The measles virus can spread effortlessly through the air when an infected person coughs, sneezes, or even breathes. It can also linger on surfaces or objects for hours, infecting individuals who come into contact with these contaminated surfaces. Dr. Bogoch highlights the contagious nature of measles, noting that even hours after an infected person has left a room, the virus can still infect someone who enters the space and is not immune to measles. This virus has an uncanny ability to target unvaccinated or under-vaccinated individuals and communities.
The Severity of Measles Complications
Measles is often misunderstood as a mild childhood illness, but it carries significant risks, especially for young children and individuals with weakened immune systems. Complications from measles can include pneumonia, brain swelling (encephalitis), permanent hearing loss, and even death. Dr. Theresa Tam, the chief public health officer of the Public Health Agency of Canada (PHAC), warns that measles is a serious illness, with approximately one in five infected children requiring hospitalization. Dr. Tam emphasizes that measles is not a trivial illness, as infected children often experience high fever, red eyes, and a characteristic rash that spreads from the face to the rest of the body. The latest data from PHAC reveals that between February 2 and February 8, 34 new measles cases were reported in Manitoba, Ontario, and Quebec, with an additional three probable cases linked to an ongoing outbreak in Ontario.
The Role of Vaccination in Preparing Against Measles
The measles vaccine is a cornerstone of disease prevention, with decades of data attesting to its safety and efficacy. In Canada, the measles vaccine is available as part of the measles-mumps-rubella (MMR) or measles-mumps-rubella-varicella (MMRV) vaccine. The first dose is typically administered to children at 12 months of age, with a second dose given at 18 months or between four and six years of age. Since its introduction in Canada in 1963, the measles vaccine has led to an over 99% reduction in measles cases. The efficacy of a single dose of the measles vaccine is estimated to be between 85% and 95%, while a second dose pushes this efficacy close to 100%. Unfortunately, vaccination rates for measles have been declining in recent years, leaving a growing number of individuals vulnerable to infection and weakening community immunity. To effectively prevent measles outbreaks, at least 95% of the population must be vaccinated.
The Factors Behind the Rise in Measles Cases
The recent surge in measles cases in Canada is attributed to a combination of factors, including the global resurgence of the virus and declining vaccination rates. A study published in the Canadian Journal of Public Health in October 2024 found that vaccination rates for the MMR vaccine declined in 2023 compared to pre-pandemic levels in 2019. Specifically, coverage for one dose of MMR dropped from 89.5% to 82.5%. The most significant declines occurred during the COVID-19 pandemic, a period marked by widespread misinformation about vaccines. This decline has continued post-pandemic, leaving an increasing number of people susceptible to infection and undermining herd immunity. Dr. Bogoch explains that missed doses, barriers to access, and misinformation have all contributed to the decline in measles vaccination rates. Additionally, the global spread of measles has led to importations of the virus into Canada, particularly in regions with pockets of unvaccinated individuals.
The Path Forward: Rebuilding Community Immunity
The resurgence of measles in Canada serves as a stark reminder of the importance of maintaining high vaccination rates. While measles vaccination rates in Canada remain relatively high, they are still below the necessary threshold for community immunity in some regions. The highly contagious nature of measles means that outbreaks can spread rapidly once they take hold, making prevention through vaccination the most effective strategy. Dr. Bogoch emphasizes that measles cases should be preventable given the effectiveness of the measles vaccine. He underscores that the vaccine is extraordinarily safe, with decades of data supporting its safety and efficacy. However, misinformation and declining vaccination rates have created vulnerabilities in the population, allowing measles to resurface. To combat this, it is crucial to address misinformation, ensure equitable access to vaccines, and encourage individuals to stay up to date on their vaccinations. By taking these steps, Canada can work towards rebuilding community immunity and preventing further measles outbreaks.
