The Science of Exceptional


Flu Avert


An effective intranasal vaccine for equine influenza virus.

  • Just one dose required for primary immunization or for a booster immunization following any other equine influenza virus (EIV) vaccine
  • Proven safe and effective even in horses immunosuppressed by long-distance transport or exercise1
  • Rapid onset of immunity ‐ just five to seven days in naive horses2
  • Recommended for use during EIV outbreaks3
  • When the vaccine replicates in the horse’s nasal mucosa, a rapid local immune response occurs. The horse develops an immune response that combats disease similar to when the horse is exposed to a virulent (disease-causing) wild strain of the equine influenza virus.
  • This vaccine is a lyophilized preparation containing an attenuated, cold-adapted, viable equine influenza virus type H3N8 strain (EIV A/Equine 2/Kentucky/91). Contains no preservatives.


This product has been shown to be effective for the vaccination of healthy horses 11 months of age or older against disease caused by EIV. Duration of immunity has been shown to be at least 6 months. For more information regarding safety and efficacy data, go to This product has been shown to be effective against virus shedding of EIV.



Administer a single 1 mL dose intranasally in one nostril. The dose is administered into the nasal passages with a special proprietary applicator attached to a luer lock syringe. For more information on revaccination frequency, consult your veterinarian.


Additional information about FLU AVERT I.N.®

Man handing woman a bucket with horse in background

Equine Product Reference Guide

A guide to the entire equine product line from Merck Animal Health.


FLU AVERT I.N. One Powerful Dose of Immunity

The Science of Exceptional


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1. Lunn DP, Steve Hussey S, et al. Safety, efficacy, and immunogenicity of a modified-live equine influenza virus vaccine in ponies after induction of exercise-induced immunosuppression. JAVMA. 2001:218(6):900-906. 2. Townsend HGG. Onset of protection against live-virus equine influenza challenge following vaccination of naive horses with a modified-live vaccine. Unpublished data. 3. AAEP Vaccination Guidelines available at