First Live-Attenuated Equine Influenza Vaccine Developed, Tested


Equine influenza virus is highly contagious, and preventing its spread can even help avert a pandemic. Now, researchers believe they have developed the first live-attenuated vaccine to do just that.

Vaccination is the most effective strategy to prevent H3N8 equine influenza virus (EIV) infection, but the currently available EIV live-attenuated influenza vaccine (LAIV) has not been updated in more than a quarter-century. Investigators from the University of Rochester have created a new LAIV that they say is safer and more effective than existing EIV vaccines.

In the journal Virology, the research team explains that its new EIV vaccine was generated using reverse genetics—making this the first EIV LAIV based on these approaches.


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“Our novel platform represents an easier and faster approach for the feasibility of implementing a safe and more effective LAIV for the prevention and control of H3N8 EIVs in the equine population,” the investigators wrote, “reducing the burden of current and future influenza disease in horses.”

Vaccine Development and Testing

By using reverse genetics, the vaccine replicates and generates an immune response in the nose, where virus first enters the body, but not in the lungs, where virus replication can cause disease. This approach thwarts the virus upon entry into the body and prevents it from entering and replicating in the respiratory tract. For this reason, the research team formulated the vaccine into an easily administered nasal spray.

To evaluate the vaccine, the investigators first tested it on 6 female mice. First, the mice were anesthetized and vaccinated with the EIV LAIV. Then, 14 days post-vaccination, each mouse was given a dose of H3N8 EIV. Results showed that the vaccine protected the mice against the H3N8 EIV strain.

The investigators also tested the vaccine on 6 horses; 4 horses were vaccinated and 2 served as controls. At 27 days post vaccination, each horse was given a dose of H3N8 EIV. Vaccinated horses showed no flu-like signs, including nasal discharge, wheezing, or coughing, when exposed to the EIV strain.

These results showed that a single spray of the EIV LAIV induced protection against the EIV strain.


Horses, pigs, dogs, and other animals can each generate new influenza strains that could infect people, meaning that preventing the spread of EIV not only helps equine health, but also the health of humans and other animals. Importantly, the use of reverse genetics allows quick updating of the vaccine should a new EIV strain emerge.

While this investigation included only a small number of horses, the results show great promise for the development of a safer, more effective EIV vaccine. According to the authors, a larger study is in the planning stages now.

“These results demonstrate the feasibility of implementing a novel EIV LAIV approach for the prevention and control of currently circulating H3N8 EIVs in horse population,” the authors wrote.

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