Vaccinations have been credited with some of humanity's greatest 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.

"probably an underestimate."

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, diphtheria and whooping cough, and then tracked the number of cases following the introduction of vaccines. As the following graph shows, the introduction of commercially available vaccines for these diseases drastically reduced the number of probable cases of disease — eliminating 95 percent of likely cases overall, according to the study. Further, that's "probably an underestimate, since we could not include all vaccine-preventable diseases," according to the study authors.

The scientists behind the work point to their findings as further evidence of the effectiveness of vaccination programs: "If you’re anti-vaccine, that’s the price you pay," said Donald S. Burke at the University of Pittsburgh Medical Center, to the New York Times. Indeed, despite the proven efficacy of vaccines, there is still a vocal minority of people who are resistant to have themselves or their children vaccinated against contagious diseases over the fear that the vaccines themselves can cause other health problems. As the study points out, "reported rates of vaccine refusal or delay are increasing," which is a major concern for public health more broadly. Whether the study convinces those few anti-vaccine outliers to reconsider their behavior remains to be seen, but at the least it should help further educate people aboard their importance.