When considering vaccines for feral cats, modified live virus (MLV) vaccines can be effective with one injection. Do we recommend them for feral cats? That depends. NOT if it means less money available for surgeries. If your money is plentiful, then consider vaccinating. If money is limited, invest it in surgery. Dollar for dollar, spay/neuter is a better investment for the cat’s health and for the futures of many, many cats.

MLV vaccines begin stimulating immunity the first day they are given. The vaccine contains viruses that replicate in the cat’s body but do not cause disease. A booster 3-4 weeks later is never required nor recommended in cats over 14 weeks of age. Another benefit is that vaccinated cats can shed attenuated vaccine virus particles in the feces. These viruses do no harm, and actually stimulate immunity in other cats/kittens coming in contact with the feces. This is potentially valuable in colonies of free-roaming cats.

The only caution with MLV vaccines is hygiene. If the vaccine accidentally gets ON the cat instead of IN the cat, then it may cause some mildly runny eyes of mild sneezing. Vaccine virus cannot cause symptoms of distemper. MLV vaccine that gets topical should be cleaned off with a swab of alcohol.