Contagious Diseases in the U.S. from 1888 to 2011

In November 2013, Donald Burke and coworkers at the University of Pittsburgh published an interesting study. The authors wanted to determine the impact of vaccines in the United States. They obtained weekly surveillance data published in the journal Morbidity and Mortality Weekly Report between 1888 and 2011. They used the year that a vaccine was licensed as the cutoff year to separate the pre-vaccine from post-vaccine period, realizing that uptake would be variable. They then multiplied the median weekly incidence rates from pre-vaccine years with population estimates for the post-vaccine years.

The authors estimated that about 103 million cases of disease had been prevented by vaccination since 1924. Of these hypothetical cases, about 26 million cases were prevented in the most recent decade included in the study (2002-2011). The disease with the most cases prevented was diphtheria (40 million cases), owing primarily to the fact that diphtheria had the second highest pre-vaccination incidence rate (237 cases per 100,000 population year) and the longest standing vaccine program. Second was measles (35 million cases), which had the highest disease incidence (318 cases per 100,000 population year).

Of interest, the disease with the most rapid decrease in the number of reported cases was measles (22% decrease each year post-vaccination). Rubella and polio were next, with annual decreases of 16% and 15%, respectively.

Perhaps more than any other, this study shows the incredible power and impact of America’s vaccine program.