Vaccinations have prevented at least 103 million cases of contagious disease since 1924

Vaccinations have been credited with some of humanity’s greatest health technological triumphs over disease, including drastically reducing polio around the globe and almost eliminating smallpox entirely. But how many people have been spared life-threatening infections thanks to the introduction of vaccines? At least 103.1 million children in the US alone since 1924, according to a new analysis of historical infection rate data going back to 1888. The study, a mammoth undertaking that tracked nearly 88 million cases of disease throughout thousands of America’s biggest cities and extrapolated all the likely additional cases had their not been vaccines, was published at the end of November in the New England Journal of Medicine. The journal article is paywalled, but the entire dataset has been made public access at the project’s website, also known as “Project Tycho,” named after Denmark astronomer Tycho Brahe. It focused on seven vaccine-preventable diseases: polio, measles, rubella, mumps, hepatitis A,...