New WHO Strategy Targets Relapsing Plasmodium Vivax Malaria Worldwide

The new WHO guidance strengthens the fight against Plasmodium vivax malaria by combining safer radical cure medicines with routine G6PD testing to prevent dangerous side effects. By clearing both blood-stage infection and hidden liver parasites, countries can reduce relapses and move closer to eliminating this stubborn form of malaria.

For many families in Asia, Latin America and the Pacific, malaria is not a one-time illness. Plasmodium vivax, one of the five parasites that cause malaria in humans, has a troubling habit of returning weeks or even months after a person seems to have recovered. Unlike the more widely known Plasmodium falciparum, this parasite can hide quietly in the liver in a dormant form. Later, without another mosquito bite, it can reactivate and cause a fresh bout of fever.

This ability to relapse makes P. vivax especially hard to eliminate. A single infection can lead to repeated illness, missed work and school, and ongoing transmission in the community. Health experts say that unless these hidden liver parasites are cleared, the cycle will continue.

The Push for a “Radical Cure”

To stop relapses, doctors must treat not only the parasites in the blood but also those hiding in the liver. This is known as a “radical cure.” For decades, the only drug that could eliminate the dormant liver stage was primaquine. While effective, primaquine usually has to be taken daily for seven or fourteen days. In remote or busy settings, completing the full course can be difficult.

In 2024, the World Health Organization recommended a new option: tafenoquine. Unlike primaquine, tafenoquine can be given as a single dose. This is a major advantage. One supervised dose is far easier for patients and health workers than a two-week treatment. Experts believe this could improve adherence and reduce the number of people who relapse simply because they did not finish their medicine.

However, both drugs come with an important safety concern that cannot be ignored.

Why Testing Matters Before Treatment

Primaquine and tafenoquine can cause serious side effects in people with a condition called glucose-6-phosphate dehydrogenase deficiency, or G6PD deficiency. This is a common inherited condition that affects red blood cells. In people with G6PD deficiency, certain medicines can trigger the rapid breakdown of red blood cells, leading to acute haemolytic anaemia.

Symptoms may include dark urine, yellowing of the eyes or skin, weakness, and shortness of breath. In severe cases, patients may need urgent medical care and even blood transfusions.

Because of this risk, the new WHO guidance strongly recommends testing for G6PD activity before giving radical cure medicines. New near-patient tests can measure enzyme levels within minutes using a small blood sample. These tests help health workers decide which treatment is safe for each patient. People with normal enzyme levels can receive standard doses. Those with lower levels may need modified regimens or closer monitoring.

This step toward safer, more personalized care is seen as a major advance in malaria treatment.

From Policy to Practice

The updated guidance is not just about medicines. It calls on countries to strengthen their health systems to support safe and effective treatment. National malaria programmes are encouraged to update their treatment guidelines, ensure new medicines and tests are approved, and improve supply chains so that clinics do not run out of essential tools.

Training is also key. Health workers need to learn how to perform G6PD tests correctly, explain the purpose of testing to patients, and recognize early signs of side effects. Supportive supervision and clear reporting systems help maintain quality and build confidence in the new approach.

Community engagement plays an important role as well. In some places, people may feel anxious about genetic testing or new medicines. Clear communication about the benefits of preventing relapse can help build trust and acceptance.

Pilot projects in countries such as Brazil, Thailand, Peru, Indonesia and Papua New Guinea have shown that combining G6PD testing with radical cure is feasible in real-world settings. These experiences are helping shape broader roll-out plans.

A Step Closer to Elimination

Plasmodium vivax has long been considered the “forgotten” malaria, less deadly but more persistent. Its ability to hide in the liver has allowed it to survive even in places where other forms of malaria have declined.

With the introduction of single-dose tafenoquine and wider access to reliable G6PD testing, health authorities now have stronger tools to tackle relapse. By treating both the visible infection and the hidden liver stage safely, countries can reduce repeated illness and cut transmission.

Experts say that if these strategies are implemented carefully and widely, the world could move closer to eliminating P. vivax malaria. For communities where malaria keeps coming back, that would mark a significant and long-awaited breakthrough.