The global pandemic isn’t the only current example of what happens when vaccine skepticism and misinformation infect the public. Childhood vaccination rates around the world are also experiencing their largest drop in three decades. And on July 21, another viral disease with remarkably effective vaccines to prevent it made a very unwelcome appearance. A single case of polio turned up in Rockland County, New York—the first time any case of polio had been detected in the U.S. in nearly a decade. The infected individual, whose name is being withheld, is a man in his twenties who recently developed polio-related paralysis. He had never been vaccinated against the disease.

A single case in a single county is a bigger deal that it may seem. Polio was declared officially era…