On Jun. 18, 2024, the Houston Zoo announced that Tess, a 40-year-old Asian elephant at the Zoo, had been given the first-ever dose of an mRNA vaccine created by virologists at Baylor College of Medicine (BCM) to prevent the deadly elephant endotheliotropic herpesvirus (EEHV) 1A—a devastating viral disease in Asian elephants worldwide.

The vaccine’s effectiveness will be measured by evaluating antibody levels in her blood while monitoring for specific side effects or adverse reactions such as injection site swelling or allergic reaction.

EEHV is the number one killer of Asian elephant calves living under managed care and poses a major threat to both Asian and African elephants in the wild. Led by Colossal Scientific Advisor, Dr. Paul Ling, this marked a historic milestone for endangered elephants everywhere.