“Spay Vaccine”: Magic Bullet or Waste of Time?


Researchers at the University of Florida have discovered that a vaccine used to sterilize wildlife could be a big help in managing feral cat colonies, too.

GonaCon causes the body to produce antibodies that reduce the ability to release sex hormones like estrogen, progesterone, and testosterone. After being vaccinated, the cat stays out of heat as long as there are enough antibodies in her system.

While anything that helps to control the population of unwanted cats in our communities is great, I think the vaccine’s developers have failed to see the big picture.

Although the research team, led by Julie Levy, DVM, Ph.D., of the Maddies Shelter Medicine Program at UF, hopes that the vaccine will be “less expensive, labor-intensive, and invasive than current methods, such as surgical sterilization,” I’m afraid that just won’t turn out to be the case.

Let’s start with the cost issue. Although GonaCon was developed by researchers at the USDA Animal and Plant Health Inspection Service National Wildlife Research Center who have no licensing agreements with the USDA or commercial drug producers, how long will that continue? If the vaccine becomes popular, how long will it be before the drug companies start seeing it as a cash cow and quickly secure a monopoly on the researchers or the patent? In the U.S., where I live, even generic versions of medications can run upward of $300 for a month’s supply … and that’s just one prescription! How many feral cat advocacy organizations, independent shelters, and vet clinics will be able to afford the drug if that happens?

Then there’s the issue of long-term effectiveness. Although the 15 cats treated with the vaccine had a 93 percent infertility rate for the first year, that decreased to 73 percent the second year. By year five, only 27 percent of the cats remained sterile. What that means to me is more work for community cat colony managers: the animals that receive the vaccine will have to be trapped every year and revaccinated or they will quickly start going back into heat. That makes the vaccine more labor-intensive for cat colony caretakers, not less.

And what about the logistics of identifying cats that have been sterilized? How will colony caretakers, shelter staff, and vets know whether a cat has received the vaccine? When cats are neutered through TNR programs, they have the tip of one ear cut off. This is the international symbol for “this cat has been spayed or neutered, vaccinated, and is under the care of a colony manager.” Since the mark is permanent, you can’t ear-tip a cat that has had a temporary sterilization. Cat colony managers and feral cat advocacy groups would have to come up with some way of showing that a cat has received the vaccine and when it was given.

Not only that, but the vaccine is only for female cats. While this pushes my political buttons in the most obscenely anthropomorphic way (why are women expected to be solely responsible for birth control?), the fact is that if male cats aren’t sterilized, they’ll still spray, fight, and roam all over the place in search of mates. This behavior is unpleasant for the people who have to deal with it, but it’s often downright fatal for the cats: If they’re not seriously injured in fights or motor vehicle accidents, or killed by human neighbors who just don’t want to put up with them, unneutered males are much more likely to spread diseases like the feline immunodeficiency virus.

GonaCon may have a place in veterinary medicine. It could be a godsend for people whose cats have medical conditions that make it too risky to anesthetize them for spay surgery. It could be a good stopgap measure for cats who go into heat before their spay surgery is scheduled. And it could be helpful for managing feral cat colonies in areas where surgery is unavailable or too far away to be practical.But with the facts I have at hand, I don’t think it has a place in the management of the vast majority of community cat colonies.

Although trap-neuter-return might be more costly in money and labor at the outset, in the long term it saves costs … and it saves cats’ lives.

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