The Impact of Childhood Vaccination Programs in the United States: Analysis of 125 Years of Weekly Disease Surveillance

BACKGROUND:   Vaccines are widely accepted as valuable public health tools that have led to the eradication of smallpox and the elimination of polio and measles in the United States. Paradoxically, the success of vaccination has decreased the perceived threat of vaccine-preventable diseases among parents leading to increased rates of vaccine refusal in certain populations across the country. This has resulted in local gaps in herd immunity and in the resurgence of preventable diseases such as measles and pertussis. In 2012, the largest pertussis epidemic in the US since 1959 occurred with 38 thousand cases reported. Contagious diseases have been reported and recorded weekly in the US since 1888, but long-term historical patterns have not previously been analyzed due to the lack of access to these data in computable form.

METHODS:   We digitized data from all US weekly surveillance reports from 1888 to the present, comprising 87,950,807 individual cases localized in space (city, county, or state) and time (week and year). The digitized historical data on smallpox, polio, measles, mumps, rubella, hepatitis A, diphtheria, and pertussis were synoptically reviewed and visualized. Using detailed data from before and after vaccine licensure, we qualified the number of cases prevented by vaccination against all selected diseases except smallpox.

RESULTS:   Displays of a century of disease elimination in the United States provided compelling illustrations of the impact of vaccination programs throughout the country. We estimated that vaccination programs against seven childhood diseases have prevented 103 million clinical cases in the US between 1924 and 2010 (10^th and 90^th percentile: 72.3 – 147.8 million cases). Of these, 26 million (25%) were prevented during the last decade. Since 1980, resurgences of measles, mumps, rubella, and pertussis occurred across the country.  This study also revealed significant spatial heterogeneity in disease elimination and resurgence patterns.

CONCLUSIONS:  This study confirms the clear historical public health value of vaccination programs in the US, provides quantitative estimates of the total number of cases of contagious diseases prevented by vaccines, and illustrates examples of previously controlled vaccine-preventable diseases that have resurged. This study also demonstrates how high-resolution public health data can be effectively used for analysis. Detailed spatiotemporal public health data have too often remained inaccessible and therefore underutilized, constraining scientific understanding of the dynamics of disease transmission and hampering disease-control programs. Open access to large disease surveillance data sets in computable form should become a worldwide norm.