Chester Zoo in England has long been at the forefront of elephant conservation.
Back in 1977, it became the first zoo in the U.K. to successfully breed Asian elephants in captivity — a milestone that sparked decades of continued commitment to the species. That dedication has only deepened as the plight of Asian elephants grows more dire.
According to the World Wide Fund for Nature, the population of Asian elephants has plummeted by more than 50% over the past three generations. Beyond threats like habitat destruction, deforestation, and poaching, the species faces another, lesser-known danger: Elephant endotheliotropic herpesvirus (EEHV).
EEHV is a fast-acting and often deadly disease that can cause severe internal bleeding, killing young elephants — especially those under eight years old — within just 24 hours of showing symptoms.
Chester Zoo experienced this tragedy firsthand in 2009 when it lost a calf to the virus. The heartbreaking event spurred the creation of the “Never Forget Campaign,” which raised £250,000 to fund critical research into a possible vaccine.
“In 2019, our calf Indali Hi-Way became one of only a few known survivors of EEHV after intensive treatment,” the zoo said in a statement. “By 2021, the first vaccine doses were administered here at Chester Zoo.”
Now, in 2025, that pioneering work has reached a historic milestone. Following the publication of successful trial results, the vaccine is ready for global rollout.
“This vaccine was first given to an elephant here in 2021,” said Dr. Katie Edwards, lead conservation scientist and co-author of the study. “But this announcement is a turning point — it means we can now use the vaccine more widely to protect elephants everywhere. EEHV has claimed countless lives, but this marks a huge step toward ending those losses.”
Falko Steinbach, professor of veterinary immunology at the University of Surrey and senior author of the research, called the breakthrough “a landmark moment” for elephant conservation.
“For the first time, we’ve shown that a vaccine can successfully trigger the immune response elephants need to defend against EEHV,” Steinbach said.
Chester Zoo’s head of veterinary services, Javier Lopez, emphasized accessibility as the vaccine moves into wider use.
“As a conservation charity, our mission is to make the vaccine open source and freely available to protect as many elephants as possible,” Lopez said. “EEHV has been a silent killer for years — now, we finally have a way to fight back.”