Active immunization against equine influenza and tetanus. Primary vaccination at 5-6 months of age and second injection 4-6 weeks later. Repeat vaccination 5 months later. Onset of immunity 14 days after primary vaccination. Duration of immunity 5 months after primary vaccination. After the initial vaccination and the booster injection 5 months later, a 1 year protection for equine influenza is achieved and 2 years for tetanus.