A fatality rate of 40 to 75 percent. No approved treatment. No vaccine. In January 2026, Nipah virus cases were confirmed in India, triggering emergency airport screenings across Asia. Now a Japanese-developed vaccine is taking a major step forward into clinical trials, aiming to stop the next pandemic before it starts.

What Is Nipah Virus? The Pathogen WHO Calls a Priority Threat

Nipah virus was first identified in 1998 during an outbreak among pig farmers in Malaysia. Named after the village of Kampung Nipah where it was discovered, the virus belongs to the Paramyxoviridae family, the same viral family as measles, and is classified under the Henipavirus genus.

The virus's natural hosts are large fruit bats, known as flying foxes. Transmission to humans typically occurs through consuming fruits or date palm sap contaminated with bat saliva or urine. In the 1998 Malaysian outbreak, pigs served as intermediate hosts, spreading the infection from bats to farmers on a devastating scale.

Once infected, symptoms begin with fever, headache, muscle pain, and vomiting before rapidly progressing to encephalitis (inflammation of the brain) and multi-organ failure. The fatality rate varies between 40 and 75 percent depending on the outbreak, staggeringly high compared to COVID-19's roughly 1 to 2 percent.

What makes Nipah particularly alarming is confirmed human-to-human transmission, especially among family members and healthcare workers caring for infected patients. The two cases confirmed in India's West Bengal state in January 2026 were both healthcare workers, likely infected by an undiagnosed patient at their hospital.

The World Health Organization has placed Nipah on its R&D Blueprint list of priority pathogens with pandemic potential. Since 1998, an estimated 750 people have been infected, and about 415 have died.

January 2026: India's Outbreak Rattles the World

On January 26, 2026, India's health authorities officially notified WHO of two confirmed Nipah virus cases in West Bengal state. Both infections were confirmed on January 13 by the National Institute of Virology in Pune. Indian authorities traced 196 close contacts, all of whom tested negative and remained asymptomatic, and declared the outbreak contained.

Despite this reassurance, the response across Asia was swift and serious. Thailand deployed health screening checkpoints at airports for passengers arriving from West Bengal. Malaysia, Indonesia, Singapore, Hong Kong, and Vietnam all strengthened border surveillance. China activated disease prevention measures in border areas, and Taiwan's Centers for Disease Control announced plans to classify Nipah as a Category 5 threat.

India is no stranger to Nipah. Since 2018, the southern state of Kerala has experienced outbreaks almost annually, including one in July 2025 that infected four people and killed two. The West Bengal cases were the state's third outbreak, following incidents in Siliguri (2001) and Nadia district (2007).

Japan's Vaccine: Using Measles Virus as a Delivery Vehicle

Currently there is no approved vaccine for Nipah virus anywhere in the world. Against this backdrop, a Japanese-developed vaccine reaching the clinical trial stage represents a significant milestone.

The vaccine grew out of research led for years by Professor Chieko Kai and her group at the University of Tokyo's Institute of Medical Science. It is a recombinant vaccine that uses a measles virus vector, and the project also draws support from SCARDA (Strategic Center of Biomedical Advanced Vaccine Research and Development for Preparedness and Response), Japan's national command center for domestic vaccine development. The team later moved its base to Teikyo University's Advanced Comprehensive Research Organization, where Professor Misako Yoneda now serves as principal investigator. After securing approval from Belgian regulators, the first participant was dosed in Belgium on June 15, 2026, in a Phase I trial testing safety in humans.

The technology behind this vaccine is called a viral vector vaccine. It uses a weakened (attenuated) measles virus as a vector, essentially a delivery vehicle, into which Nipah virus genes have been inserted. When injected, the body produces some of Nipah virus's surface proteins, prompting the immune system to generate antibodies. If the vaccinated person later encounters the real Nipah virus, their immune system can respond quickly to prevent illness.

Why measles? Because the measles virus is renowned for inducing what scientists call lifelong immunity, an exceptionally strong and durable immune response. Attenuated measles virus has been used worldwide for decades as the basis for measles vaccines, with an extensive safety and efficacy track record.

Kai and her colleagues have been developing this recombinant vaccine platform since around 2010. In animal studies using hamster and primate infection models, the vaccine demonstrated complete protective efficacy against lethal Nipah virus challenge.

Global Collaboration With CEPI Backing

The project has received up to about $31 million (roughly ¥3.44 billion) in funding from CEPI (Coalition for Epidemic Preparedness Innovations), an international partnership established at the 2017 World Economic Forum in Davos and funded by the governments of Norway and India, the Bill & Melinda Gates Foundation, and the Wellcome Trust.

This is a genuinely global collaboration. Manufacturing is handled by the Netherlands-based Batavia Biosciences. Phase I and Phase II clinical trials are planned in partnership with the European Vaccine Initiative (EVI), Stanford University in the United States, and the International Centre for Diarrhoeal Disease Research (icddr,b) in Bangladesh, a country directly affected by recurring Nipah outbreaks.

On the domestic front, the Japanese government has significantly strengthened its vaccine development infrastructure. SCARDA, established within AMED (Japan Agency for Medical Research and Development), has designated Nipah virus infection as one of Japan's priority infectious diseases and promotes industry-academia-government research collaboration. Through the World-Class Research and Development Center for Vaccine Development initiative launched in 2022, the University of Tokyo's Next Generation Infectious Disease Center serves as a flagship hub, coordinating efforts across Japan's research institutions.

The Global Race for a Nipah Vaccine

Japan's vaccine isn't the only contender in the fight against Nipah. Multiple approaches are advancing simultaneously worldwide.

The most advanced candidate is the University of Oxford's ChAdOx1 NipahB vaccine, built on the same viral vector platform as the Oxford/AstraZeneca COVID-19 vaccine. Phase I trials began in the UK in January 2024, with 51 participants safely completing one year of follow-up. In December 2025, the world's first Phase II trial for a Nipah vaccine launched in Bangladesh, enrolling 306 healthy adults. Funded by CEPI with manufacturing support from the Serum Institute of India, this trial also established an investigational reserve of up to 100,000 doses for potential emergency deployment. The European Medicines Agency granted the vaccine PRIME (PRIority MEdicines) designation in June 2025.

Meanwhile, Moderna in the U.S. is advancing an mRNA-based Nipah vaccine (mRNA-1215) through Phase I trials, and India's Gennova Biopharmaceuticals is developing a self-amplifying mRNA candidate with CEPI funding.

Japan's Unique Strengths in This Fight

Among these competing candidates, Japan's approach carries distinctive advantages.

First, the measles virus vector. Measles vaccines have been administered billions of times globally, giving this platform an unusually deep safety record. The near-lifelong immunity that measles virus induces could also provide long-lasting protection without booster shots, a crucial advantage for a disease that strikes sporadically and unpredictably.

Second, Japan's strategic rebuilding of its vaccine development capabilities. During the COVID-19 pandemic, Japan lagged in domestic vaccine development. Learning from that experience, the country has moved quickly to establish SCARDA and new research hubs. The Nipah vaccine trial serves as a proving ground for this new infrastructure.

Third, Japan's role as a hub for international cooperation. The project connects institutions across Europe, the United States, and South Asia in a genuinely global research network, leveraging each partner's strengths.

Why This Vaccine Matters Now

Nipah outbreaks have been small and sporadic so far, but experts' greatest fear is a mutation that enhances human-to-human transmissibility. Nipah belongs to the same viral family as measles, one of the most contagious diseases known. If Nipah acquired measles-level transmissibility while keeping its 40 to 75 percent fatality rate, the consequences would be catastrophic.

Fruit bats' range spans Asia, Africa, and Madagascar, placing over 2 billion people in potential contact zones. Climate change and deforestation are increasingly pushing bat habitats into areas of human settlement, raising the risk of future spillover events.

CEPI has built a roughly $150 million Nipah R&D portfolio and set a 100 Days Mission, a goal to deliver vaccines within 100 days of identifying a new outbreak pathogen. Japan's vaccine entering clinical trials is a concrete step toward that kind of preemptive preparedness.

Japan has never recorded a domestic Nipah virus case, though fruit bats inhabit the country's southwestern islands and the risk of imported cases cannot be dismissed entirely. Pandemic preparedness isn't just a local concern. It's a global responsibility.

How prepared is your country for emerging infectious diseases like Nipah? What do you think about investing in vaccines before a pandemic strikes? Share your thoughts in the comments.

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