The Global Threat of Measles: A History and Current Crisis

Measles, a highly contagious viral infection, once posed a catastrophic threat to children worldwide. Before the introduction of the measles vaccine in 1963, nearly every child contracted the disease, and over 2 million died annually. The vaccine dramatically altered this trajectory, reducing cases by over 95% in the United States by 1968 and substantially decreasing incidence in Canada as well.

Despite this success, measles remains a significant global health challenge. Approximately 100,000 children still succumb to the disease each year, primarily in low-income countries with limited access to vaccination. The World Health Organization (WHO) categorizes a country’s progress against infectious diseases using three labels: controlled, eliminated, and eradicated. Elimination signifies the absence of sustained local transmission, relying on imported cases.

Canada initially achieved measles elimination in 1998, a milestone confirmed by the Pan American Health Organization (PAHO). The United States followed suit two years later. By 2016, all countries in the Americas had reached this status. However, outbreaks in Brazil and Venezuela led to a temporary loss of regional elimination in 2018, regained in 2024. Now, Canada has once again fallen from grace, a worrying sign for the Americas and the world.

What Does ‘Measles-Free’ Actually Mean?

Achieving measles elimination requires at least one year without ongoing local transmission of the virus. A single chain of person-to-person spread lasting longer than a year results in the loss of this status. Maintaining high vaccination rates – around 95% of the population – is crucial to preventing outbreaks and sustaining elimination.

The recent decline in childhood vaccination rates, particularly during and after the COVID-19 pandemic, has created vulnerabilities. In Canada, vaccination coverage among 2-year-olds dropped from approximately 90% in 2019 to around 82% in 2022 and 2023. This decrease directly correlated with a surge in measles cases. From just 16 cases nationwide between 2020 and 2023, Canada experienced over 100 cases in 2024 and more than 5,000 in 2025, with cases reported in every province and tragically, two infant deaths. Fewer than 10% of those infected had been vaccinated.

This situation isn’t unique to Canada. The United States and Mexico are also facing sustained outbreaks and are likely to lose their measles-free designations in 2026. While over 90% of kindergartners in the U.S. are vaccinated, this level is insufficient to prevent outbreaks. A Texas outbreak that began in January 2025 infected over 760 people and resulted in two fatalities. Nationally, over 1,600 Americans have contracted measles in 2025, the highest number since 1992, with over 90% unvaccinated.

Mexico is also grappling with thousands of cases, predominantly among unvaccinated individuals. While Central America, South America, and the Caribbean currently maintain their measles-free status, the outbreaks in North America pose a risk of wider regional spread.

Did You Know? Measles is so contagious that if one person has it in a room of 100 unvaccinated people, 90 of those people will likely become infected.

The Root of the Problem: Declining Trust and Vaccine Hesitancy

The loss of measles elimination status isn’t merely a public health failure; it’s a symptom of a broader societal issue: declining trust in scientific and health messaging. This erosion of trust has contributed to decreased vaccination rates and increased vulnerability to preventable diseases. Research suggests the issue isn’t necessarily a distrust of vaccines themselves, but rather a lack of clarity about who to trust for accurate health information.

What role does social media play in the spread of misinformation about vaccines? And how can public health officials rebuild trust with communities hesitant about vaccination?

Frequently Asked Questions About Measles