As of December, 2015, new vaccination rules were effective for horses showing in United States Equestrian Federation events. All horses showing in USEF events must be currently vaccinated for equine influenza virus and equine herpes virus. A current vaccination means the vaccine must have been given within the last six months. Both of these diseases are highly contagious and both cause respiratory symptoms, although equine herpes virus 1 can also cause abortion and neurological disease. There are herpes virus vaccines approved to protect against the abortion form of the disease but none are licensed to protect against the neurological form. Regardless, the USEF's goal is to prevent these respiratory infections from going through a show barn and infecting all the horses. The rule states that horses not in compliance may be required to leave the show grounds.

Documentation to prove your horse is vaccinated will require a veterinarian's record with the date the vaccine was given and the name of the vaccine. Also, if a person other than a veterinarian gives the vaccines, the owner must provide a receipt of the vaccine purchased that is signed by the owner or agent, name, serial number and expiration date of the vaccine and date the vaccine was given. If there is a medical reason the horse cannot be vaccinated, a letter from the veterinarian must accompany the horse and a log of temperatures taken twice daily for a week and twice daily at the show grounds must be provided. Since most show horses are routinely vaccinated for these diseases anyway, complying with this rule should not be a problem for most horse owners.