Prophylaxis is by vaccination. Active immunity is by inoculation of b-propiolactone inactivated egg-grown equine 1 and 2, with alhydrogel as an adjuvant. Some vaccine manufacturers have had to withdraw certain vaccines and compensate owners when a more powerful oil-based adjuvant caused cold abcesses at the site of injection. Expensive vaccines containing Iscoms of purified virus haemagglutinin have been developed instead of BPL-virus..

In 1998 horses which had received a vaccine containing aeuropean-like H3 virus became infected. With a new american-like virus with limited crossreactivity by HI tests to the european vaccine viruses . Vaccine manufacturers have now added an old UK American-like strain called Newmarket1/1993 to their equine 2 european-like isolates.