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University of Pittsburgh Schools of the Health Sciences

​University of Pittsburgh Researchers Develop Virus for First Intranasal Equine Influenza Vaccine

PITTSBURGH, November 23, 1999 — Julius Youngner, Sc.D., distinguished service professor and Patricia Whitaker-Dowling, Ph.D., associate professor, both in the department of molecular genetics and biochemistry at the University of Pittsburgh School of Medicine, have developed the live, attenuated virus used in the first equine intranasal influenza vaccine. Scientific literature reports tests of a human vaccine based on the same technology. These human studies have been underway for approximately 10 years at institutions outside of the University of Pittsburgh and a human intranasal flu vaccine may be available in the near future.

Dr. Youngner’s work spans nearly five decades, and his achievements include working with the late Jonas Salk, M.D., at the University of Pittsburgh in the development of the first vaccine against poliomyelitis in the 1950s.

The Pittsburgh researchers also worked in collaboration with investigators from the Heska Corporation of Fort Collins, CO, which will be manufacturing and marketing this new product, Flu Avert I.N. vaccine, to equine veterinarians.

"The majority of upper viral infections in horses can be attributed to equine influenza," Dr. Youngner said. "Previous vaccines were killed virus injectable vaccines, which have been shown to leave horses vulnerable to equine influenza, even when horses are vaccinated up to six times a year."

"We are very pleased to have U.S.D.A. approval and look forward to marketing this product," said Robert Grieve, Heska chief executive officer. "The equine influenza vaccines currently on the market simply do not afford the degree of protection needed by horse owners today. We believe Flu Avert I.N. vaccine affords an unprecedented level of protection in the prevention of equine flu. This will be especially important to the owners of performance horses that regularly come into contact with the other horses."

Equine influenza is a serious disease in horses. Although infections are not usually life threatening, the disease is evidenced by coughing, fever, lack of appetite and tracheobronchitis, which can often lead to secondary bacterial pneumonia. It is recommended to owners that horses rest for at least three weeks following an influenza attack.

The studies involved more than 600 horses at locations throughout North America to verify both the safety and efficacy of Flu Avert I.N. vaccine. Previously, vaccines were licensed based on their ability to stimulate an antibody titer. These titers have been shown to decrease quickly and do not necessarily correlate with protection in the face of an outbreak. Flu Avert I.N. vaccine was tested in a challenge model in which both vaccinated horses and controls were heavily exposed to wild-type equine influenza virus. While the non-vaccinated horses showed the typical clinical signs of cough, fever, nasal discharge, poor appetites and depression, vaccinated horses were completely protected from clinical signs at three months and still demonstrated significant protection at six months and one year after vaccination.

"The cold-adapted virus used in the vaccine has a big advantage of replicating only at the temperature found in the upper respiratory tract," Dr. Whitaker-Dowling explained. "It produces the kind of immunity that a natural infection would, but doesn’t make the animal sick."

Vaccination requires a small 1ml dose that is administered into one nostril. Administration of the vaccine is safe and painless, allowing horses to avoid the risk of injection site reactions and muscle soreness associated with vaccines that are administered with a needle.

Additional information on Flu Avert I.N. vaccine is available through Heska’s web site at


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