We’ve developed the world’s first elephant virus vaccine
A groundbreaking new vaccine - the first of its kind - can now be rolled out globally to help in the battle against a deadly virus that has devastated endangered elephant populations.
Developed by our team at Chester Zoo, together with the University of Surrey and the Animal and Plant Health Agency (APHA), the vaccine targets elephant endotheliotropic herpesvirus (EEHV), one of the most serious threats facing young Asian elephants worldwide.
The breakthrough has been published today in the prestigious journal Nature Communications.
In a landmark proof-of-concept trial, we showed that the vaccine is safe and effective in triggering a strong immune response - a crucial step toward preventing EEHV, a disease that can kill elephants in just 24 hours.
EEHV poses a severe threat to the survival of Asian elephants, a species already listed as Endangered on the IUCN Red List, with fewer than 40,000 individuals remaining in the wild. Fatal cases have been documented across India, Nepal, Myanmar, Thailand and beyond - with the disease affecting both wild populations and vital conservation breeding programmes in zoos worldwide. The virus has also been detected in African elephants.
Indali Hi-Way (left), born at Chester Zoo in 2016, is one of only a handful of recorded survivors of EEHV after intensive treatment in 2019.
This vaccine was first delivered to an elephant here at Chester Zoo in 2021, but this publication marks a watershed moment - it means we can now say the vaccine is ready for wider use. EEHV has taken the lives of so many elephants, but this offers hope and a massive step towards ending those losses.
Dr Katie Edwards, our Lead Conservation Scientist and co-author of the study
Scientists at the University of Surrey and the Animal and Plant Health Agency have also hailed the breakthrough as a landmark moment in the global fight against EEHV.
“This is a landmark moment in our work to develop safe and efficacious vaccines. For the first time, we have shown in elephants that a vaccine can trigger the type of immune response needed to protect them against EEHV,” said Dr Falko Steinbach, Professor of Veterinary Immunology at the University of Surrey and senior author of the study.
Dr Tanja Maehr, from the Animal and Plant Health Agency, a lead author of the study and a former Chester Zoo Conservation Scholar, said:
“Our findings give real hope that vaccination can become a practical tool for preventing severe disease and death due to EEHV. The next step could be to trial the vaccine in more calves and in range countries so we can begin to protect those most at risk.”
A six-year study involving a small group of elephants confirmed the vaccine’s safety and its ability to stimulate a protective immune response. The next phase could see a careful rollout to more elephants, prioritising young individuals who are most at risk of developing the disease.
Unlike other EEHV vaccines currently in development, the ‘ingredients’ in this new vaccine focus on T-cell activation – the body’s immune system ‘generals’ that identify and destroy infected cells.
We and our partners at Surrey University and APHA chose this T-cell-based approach using proven vaccine delivery methods. The vaccine is given via injection with booster doses, making it suitable for use in zoos and sanctuaries, with plans already underway to develop delivery methods for wild populations.
As a conservation charity, our goal is for the vaccine to be open source and freely available to help save as many elephants as possible. Until now, EEHV has been a silent killer - with this vaccine, we finally have a weapon to fight back.
Dr Javier Lopez, our Head of Veterinary Services
For us, this breakthrough has been more than a decade in the making. We lost our first elephant calf to EEHV in 2009. In 2013 we launched our Never Forget campaign, raising almost £250,000 for vital research. In 2019 our calf Indali Hi-Way became one of only a handful of recorded survivors after intensive treatment. By 2021 the first doses of this vaccine were trialled here at the zoo - and now, in 2025, with trial results published, the vaccine can be rolled out worldwide.
