Hours after Donald Trump began his second term as United States president on Jan. 20, 2024, he signed an executive order to end American membership in the World Health Organization (WHO) after one year. This restarted a process that the first Trump administration initiated in July 2020 but was reversed by Joe Biden.
The withdrawal is set to take effect this week, although WHO officials may not officially accept it because the U.S. has unpaid dues from the last two years. No matter how events play out, the rift signals the start of an uncertain new era in global public health.
In the withdrawal announcement, the Trump administration cited the WHO’s “mishandling” of the COVID-19 pandemic and its inability to remain independent from the political influence of member states. This reflected Trump’s belief that the WHO leadership favoured China in early 2020 by praising its initial COVID response while faulting the U.S. for closing its border to Chinese travellers.
Other observers acknowledged the need for reform of the WHO’s cumbersome bureaucratic structure and criticized its inability to translate scientific research about COVID into useful guidance about masking and social distancing.
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Such criticisms should not obscure the WHO’s enormous contribution to global health or how U.S. interests have been intertwined with its successes. Viewed historically, its great strength lies in sustained collaboration rather than short-term emergency response.
Vaccine diplomacy
In my research for Epidemics and the Modern World and its forthcoming revision, I have explored how the U.S. conducted “vaccine diplomacy” in developing countries. After the Second World War, the U.S. discerned an alignment between its strategic objectives and the soft power it gained from campaigns against epidemic diseases and childhood immunization programs.
For example, in 1967, American funding and leadership encouraged the start of the WHO’s Intensified Smallpox Eradication Program (ISEP) in African countries. This work involved collaboration with global rivals such as the Soviet Union, which contributed large quantities of freeze-dried smallpox vaccine.
When the ISEP began, at least 1.5 million people worldwide died from smallpox annually. Only 13 years later, the WHO declared the disease eradicated from nature in 1980. This success encouraged efforts to eradicate polio, which accelerated after 1988 when the WHO launched the Global Polio Eradication Initiative with support from the United States Centers for Disease Control and Prevention and other partners.
Another important collaboration began in 1974 when the WHO and international partners launched the Expanded Program on Immunization to help prevent six childhood diseases (polio, diphtheria, pertussis, tuberculosis, measles and tetanus).
After 1985, the United States Agency for International Development (USAID) invested billions of dollars in the program. Global childhood immunization levels reached 80 per cent by the early 1990s and continued to pay health dividends thereafter.
An analysis published last year in the Lancet estimated that, in the last 20 years, USAID-funded programs had helped prevent over 90 million deaths globally, including 30 million deaths among children.
Dismantling global influence
In public health, as in other arenas, the Trump administration has discarded participation in global alliances and instead sought bilateral agreements with other countries.
By July 2025, the Trump administration had formally dismantled USAID and cancelled funding for more than 80 per cent of its programs. Modelling conducted by Boston University epidemiologist Brooke Nichols suggests the lapsed programs have already caused roughly 750,000 deaths, mostly among children.
The U.S. has also already begun to cede influence over the objectives of global health programs. At the World Health Assembly in May 2025, the U.S. did not sign the WHO Pandemic Agreement intended to foster collaboration among governments, international agencies and philanthropies after the COVID-19 pandemic.
At that same meeting, China pledged to increase its voluntary contributions to the WHO to US$500 million over the next five years. Practically overnight, China will replace the U.S. as the WHO’s largest national contributor and undoubtedly steer priorities in global health programs towards its interests.
Disease monitoring and global threats
A more immediate concern is the disruption to surveillance for ongoing disease challenges and emergent threats.
Since 1952, the WHO’s Global Influenza Surveillance and Response System has provided a platform for monitoring of cases and the sharing of data and viral samples. Information from institutions in 131 countries contributes to recommendations for the composition of seasonal influenza virus vaccines. The U.S. may be left out of this global system, which will hamper efforts to match vaccines to the circulating strains of flu.
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The WHO also dispatches response teams around the world for outbreaks of numerous diseases such as mpox, dengue, Ebola virus disease or Middle East respiratory syndrome. The exclusion of American scientists will hamper these efforts and diminish the nation’s capacity to protect itself.
The policy shift in the U.S. poses challenges for Canada both as its northern neighbour and as a strong financial supporter of the WHO. The recent spread of measles within Canada, which resulted in loss of the country’s elimination status, reminds us that disease outbreaks are inevitable but progress in public health is not.
Renewed support of the WHO and other multilateral efforts, although desirable, should be matched by expanded investment in programs for disease surveillance and research, vaccine procurement and public health communication. Federal and provincial governments and the Public Health Agency of Canada will all have roles to play as Canada faces disease threats in a rapidly changing world.
Mitchell L. Hammond, Assistant Professor of History, Western University