The World Health Organization coordinates some of the largest clinical trials on the planet and maintains the only global database that tracks trials across countries and registries. Whether you’re looking for a specific trial, trying to understand how WHO tests new treatments, or want to know how global trials differ from national ones, WHO plays a central role in how experimental medicines and vaccines reach people worldwide.
What WHO Actually Does With Clinical Trials
WHO operates on two tracks when it comes to clinical trials. First, it runs its own large-scale studies, testing drugs and vaccines for diseases that disproportionately affect low- and middle-income countries. Second, it maintains a platform called the International Clinical Trials Registry Platform (ICTRP) that pulls together data from national registries around the world into one searchable portal. This means every registered trial, whether it’s run by a pharmaceutical company in Switzerland or a government health agency in Kenya, can be found in one place.
The ICTRP connects primary registries (national databases that meet WHO’s data quality standards) and partner registries into a single network. ClinicalTrials.gov, the massive U.S.-based registry most people are familiar with, is one of many registries feeding into this system. The goal is transparency: making it impossible to quietly bury a trial that produced unfavorable results.
The Four Phases of a Clinical Trial
WHO defines four phases of biomedical clinical trials, each building on the last:
- Phase I tests a new drug for the first time in a small group of people. The goal is to find a safe dosage range and identify side effects, not to prove the treatment works.
- Phase II expands to a larger group. The treatment passed initial safety screening, but researchers now monitor for adverse effects that only show up in more people.
- Phase III scales up further, often across multiple countries and regions. This is typically the final step before a treatment gets approved.
- Phase IV happens after a country has already approved a treatment. These studies track how it performs in a much wider population over a longer period, catching rare side effects or long-term patterns that shorter trials miss.
Most people hear about Phase III trials in the news because they produce the headline results that lead to regulatory approval. But Phase IV monitoring is equally important. A drug that looks safe in 10,000 trial participants can reveal problems when given to millions.
The Solidarity Trial: WHO’s Largest Drug Study
The most prominent example of a WHO-run trial is the Solidarity trial, launched during the COVID-19 pandemic. It was designed to test multiple treatments simultaneously across dozens of countries, a structure that let researchers get answers far faster than traditional single-drug trials would allow.
The initial phase tested four repurposed drugs: remdesivir, hydroxychloroquine, lopinavir, and interferon. Results showed that all four had little or no effect on hospitalized COVID-19 patients. Rather than ending there, WHO launched Solidarity PLUS, adding three new candidates: artesunate (an antimalarial), imatinib (a cancer drug), and infliximab (an immune-modulating treatment). This adaptive design, where failed treatments are dropped and new ones added, became a model for how to run pandemic-speed research without cutting corners on evidence.
The Malaria Vaccine Program
WHO’s clinical trial work extends well beyond pandemics. One of its most significant achievements is the RTS,S malaria vaccine, which went through Phase III trials showing it reduced malaria cases by more than 50% during the first year after vaccination, the period when children face the highest risk of illness and death.
Between 2019 and 2023, WHO coordinated a massive real-world pilot program called the Malaria Vaccine Implementation Programme, delivering the vaccine to more than 2 million children in Ghana, Kenya, and Malawi. The results went beyond what clinical trials alone could show: a 13% drop in mortality among age-eligible children, substantial reductions in hospitalizations for severe malaria, and improved access to at least one malaria prevention tool for more than 90% of children. When given seasonally in areas with highly seasonal transmission, both the RTS,S vaccine and a newer malaria vaccine reduce cases by about 75%.
Ethics in Global Research
Running trials in low-income countries raises serious ethical questions. Can participants truly give informed consent if they have limited access to healthcare otherwise? Who benefits from the results? WHO partnered with the Council for International Organizations of Medical Sciences (CIOMS) to create international ethical guidelines specifically addressing these situations.
The most recent version, published in 2016, emphasizes that research must have both scientific and social value. It includes specific provisions for research in low-resource settings, protections for vulnerable groups, and rules governing how biological samples and health data can be used. These guidelines operationalize the principles in the Declaration of Helsinki, the foundational document for medical research ethics, and translate them into practical standards for the places where ethical risks are highest.
Reporting Requirements and Transparency
One of WHO’s core positions is that all clinical trial results should be publicly disclosed, regardless of whether the outcomes were positive or negative. This matters because selective reporting, where companies or researchers publish favorable trials and quietly shelve disappointing ones, distorts the medical evidence that doctors and regulators rely on.
WHO’s framework for best practice in clinical trials has three pillars: universal prospective registration (registering the trial before it starts, so it can’t disappear), public disclosure of all results, and data sharing. On the data sharing front, WHO supports including data sharing plans in trial registrations from the beginning, signaling to participants and the public that individual-level data will eventually be made available to other researchers in a de-identified form.
For reporting timelines, policies vary by country and funder. Under U.S. rules, for instance, investigators must submit summary results within one year of a trial’s completion date. Certain extensions allow delays of up to two years in specific circumstances. WHO pushes for these timelines to be universal, though enforcement remains uneven across countries.
How to Search for WHO-Tracked Trials
If you want to find a clinical trial, the ICTRP search portal at who.int lets you look across multiple national registries at once. You can search by disease, treatment, country, or registration number. For trials based in the United States, ClinicalTrials.gov remains the most detailed single-country resource, but the ICTRP is the only tool that aggregates trials registered in different countries into a unified search.
The ICTRP website also lists all primary registries in its network, partner registries, and registries that operate outside the network. If you’re looking for a trial in a specific country, checking whether that country has a primary registry on the ICTRP list can point you toward more detailed local information, including trials that may not yet appear in the global search.