Their names are Sanjay and Kabir, and their story represents one of the most remarkable conservation victories in recent memory. These two young Asian elephants at the Cincinnati Zoo and Botanical Garden have become the first elephants to survive natural Elephant Endotheliotropic Herpesvirus (EEHV) infections after receiving the world’s first mRNA vaccine designed to prevent the virus from progressing to fatal stages.
When Sanjay and Kabir arrived in Cincinnati from Dublin Zoo in 2023, they carried no protection against one of the deadliest threats facing their species. Today, they stand as living proof that innovative partnerships between biotechnology companies like Colossal Biosciences and traditional conservation organizations can prevent fatal disease progression and reshape the future of species preservation.
A Journey from Vulnerability to Protection
The story begins in 2023 when four elephants made the transatlantic journey from Dublin Zoo to their new home in Cincinnati. Among them were Sanjay and Kabir, two young males whose playful energy and curious nature quickly endeared them to their keepers. However, routine testing conducted by Baylor College of Medicine’s EEHV serology laboratory revealed a troubling reality: both elephants lacked maternal antibodies against EEHV, leaving them vulnerable to a virus that proves fatal in 60-80% of infected juvenile elephants.
For the Cincinnati Zoo’s animal care team, this discovery meant implementing extraordinary protective measures. The zoo developed an in-house EEHV PCR laboratory specifically to monitor for the virus in the young elephants’ blood—a level of surveillance that reflects both the dedication to their care and the severity of the threat they faced.
Understanding that prevention offered the best hope for managing EEHV in Sanjay and Kabir, the zoo administered plasma transfusions from elephants with antibodies to the virus. While this provided some protection, the transfused antibodies didn’t reach levels comparable to those found in elephants who had survived natural infections. The two young elephants remained at risk.
A Groundbreaking Intervention
Hope arrived in the form of a revolutionary mRNA vaccine developed through an unprecedented partnership between the Houston Zoo, Baylor College of Medicine, and Colossal Biosciences. Dr. Paul Ling, a virologist at Baylor College of Medicine and the world’s leading EEHV researcher, had spent years developing this breakthrough treatment in collaboration with the Houston Zoo.
The vaccine represented more than just medical innovation—it embodied a new approach to conservation that brings together traditional animal care expertise with cutting-edge biotechnology. Colossal Biosciences, known primarily for its de-extinction pursuits and the advanced sequencing of the dire wolf, contributed crucial support alongside other partners including Dr. Jeroen Pollet of the National School for Tropical Medicine, the International Elephant Foundation, and the Houston Methodist Center for RNA Therapeutics.
The Cincinnati Zoo became one of the first institutions to adopt this revolutionary vaccine, administering it to Sanjay and Kabir in Fall 2024. The decision required courage and conviction from their caregivers, who understood they were participating in a historic moment that could change elephant conservation forever.
The Moment of Truth
The vaccine’s effectiveness was tested in the most challenging way possible: through natural exposure to the virus it was designed to manage. In February 2025, the zoo’s in-house laboratory detected that Sabu, a herd mate, was shedding EEHV in his trunk secretions—creating an environment where transmission was not just possible but likely.
Within days, monitoring revealed low levels of the virus in Sanjay’s blood, signaling the beginning of what typically becomes a life-threatening infection. Under normal circumstances, this discovery would have triggered immediate aggressive medical intervention and grave concern for the young elephant’s survival.
Instead, something remarkable happened. The vaccine successfully prevented the virus from progressing to fatal stages. While carrying the virus, Sanjay remained healthy, with all his other blood values staying within normal ranges and never developing the severe symptoms typically associated with EEHV infection. His viral levels remained low and eventually cleared completely, while his antibody levels continued to rise—clear evidence that his immune system, strengthened by vaccination, was successfully suppressing the virus.
Soon after, Kabir also showed signs of mild EEHV infection, following the same pattern as his companion. Like Sanjay, the vaccine helped prevent progression to severe disease, demonstrating consistent effectiveness in managing this latent herpesvirus.
A Team Effort Prevents Fatal Outcomes
The successful protection of Sanjay and Kabir resulted from the dedication and expertise of numerous individuals working across multiple institutions. Dr. Mike Wenninger, director of animal health at the Cincinnati Zoo, expressed the team’s gratitude: “This vaccine, created by Baylor College of Medicine and Houston Zoo, is a tremendous source of hope for the future of Asian elephants, both in zoos and in the wild. We are incredibly grateful for this collaboration and that it helped prevent fatal progression in Sanjay and Kabir.”
The achievement also highlighted the value of institutional partnerships in conservation work. “This is a powerful example of what can be achieved through collaboration among AZA-accredited zoos,” noted officials from both the Cincinnati and Houston Zoos. The success required not just scientific innovation but also institutional commitment to trying new approaches and sharing resources across organizational boundaries.
Colossal’s involvement brought additional resources and expertise to the effort, demonstrating how biotechnology companies can contribute meaningfully to immediate conservation challenges. The same genetic technologies the company develops for de-extinction research proved valuable for protecting living endangered species facing current threats.
Beyond Individual Lives
While Sanjay and Kabir’s survival represents a personal victory for their caregivers and a triumph for the institutions that protected them, their story carries implications far beyond individual lives. These two elephants have become the proof of concept for a vaccine that could dramatically improve survival rates for Asian elephants worldwide by preventing EEHV from progressing to fatal stages.
Their successful protection marks the first documented instances of natural EEHV exposure following vaccination, providing concrete evidence that this approach can prevent severe disease progression. For a species struggling with multiple conservation challenges—habitat loss, human-wildlife conflict, and declining populations—managing the threat of EEHV represents a significant step toward recovery.
The broader impact extends to conservation philosophy and practice. Sanjay and Kabir’s story demonstrates that innovative biotechnology and traditional conservation approaches can work together to achieve results neither could accomplish alone. Their survival validates investment in cutting-edge research while honoring the fundamental commitment to individual animal welfare that drives conservation work.
It’s important to note that EEHV is a latent herpesvirus, meaning the virus remains in the body and can potentially recur. However, this breakthrough in managing EEHV represents a major milestone in conservation medicine with implications for broader wildlife disease prevention.
Living Symbols of Hope
Today, as Sanjay and Kabir continue to grow and thrive at the Cincinnati Zoo, they carry significance beyond their individual lives. They represent the potential for human ingenuity to solve conservation challenges that once seemed insurmountable. Their playful interactions with their herd mates and continued healthy development serve as daily reminders that bold scientific collaboration can yield extraordinary results.
Their story also embodies the changing landscape of conservation science, where partnerships between biotechnology companies, research institutions, and zoos are creating new possibilities for species protection. The same technologies being developed to bring back extinct species are proving valuable for preventing current extinctions.
Matt James, Executive Director of the Colossal Foundation and Colossal’s Head of Animal Operations, captured the broader significance: “In the wild, elephants are a critical keystone species, a key player in maintaining the biodiversity and health of the ecosystems they inhabit. Disruptive conservation methods rooted in genetics complement existing preservation efforts, and ensure a future for all elephants to thrive.”
A Legacy of Innovation
As Sanjay and Kabir continue their lives at the Cincinnati Zoo, their experience will inform future conservation efforts for Asian elephants around the world. The vaccine that helped prevent fatal progression in their cases is already being prepared for broader distribution, with the potential to protect elephant populations in zoos and eventually in wild habitats across Asia.
Their story serves as inspiration for continued innovation in conservation science, demonstrating that seemingly impossible challenges can yield to human determination and collaborative effort. In a field often dominated by stories of loss and decline, Sanjay and Kabir represent something different: proof that conservation victories are possible when science, dedication, and resources unite around a common goal.
The two young elephants who once faced a deadly threat now embody hope for their entire species. Their survival stands as testament to what becomes possible when we refuse to accept extinction as inevitable and instead choose to fight for every individual life that could contribute to species recovery. In the end, Sanjay and Kabir’s greatest contribution may not be their individual survival, but their role in proving that the future of endangered species can be brighter than we once dared to imagine.
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