Vaccines and the Boanthropy Risk

I’m reading Jeffrey Kacirk’s delightful Forgotten English, which includes this anecdote concerning boanthropy, a condition where a person believes himself to be a cow or ox:

In 1792, Edward Jenner successfully developed a vaccine for smallpox by injecting a boy with closely related cowpox germs. He did this despite his medical critics’ attempts to scuttle his project by circulating boanthropy scare-stores. The critics alleged that those inoculated would develop bovine appetites, make cowlike sounds, and go about on four legs butting people with their horns…