Measles Vaccination and Human Capital Development in the United States

The development of vaccines since the late 19^th century is one of the most important advancements in public health. Vaccines reduce the burden of infectious disease in a population through both a direct effect for the individual receiving the vaccine and herd immunity in the community. Although several studies document the improvements in health resulting from the introduction of vaccines, particularly in developing countries, very few have investigated the effects of these vaccines on human capital development. This study aims to fill this gap by evaluating changes in human capital development, as measured by health and education, after the introduction of the measles vaccine in the United States.

While measles has been considered eliminated in the United States since 2000, it is not eradicated and remains a threat for unvaccinated populations (either through choice or medical necessity). Recent outbreaks have received significant media attention, as people exposed abroad brought the measles virus to the United States. Understanding the potential long-run gains from worldwide eradication can shape future policy debates. In particular, my research can inform policy makers as to the value of attaining herd immunity, and ultimately eradication, for measles.

The measles vaccine was introduced in 1963; in the United States take-up of the vaccine occurred quickly and was universal, leading to reductions in morbidity and mortality. New biological evidence on how the measles virus interacts with our immune system indicates the impact of the measles vaccine may be underestimated.

I use a difference-in-difference identification strategy, taking advantage of cross-area differences in pre-vaccine measles incidence rates, with the introduction of the vaccine in 1963 as an exogenous policy change. Areas across the country have different pre-vaccine reported incidence rates of measles due to population density. When the measles vaccine was introduced in the United States there were mass vaccination initiatives resulting in universal take-up and near full reductions in incidence rates. Areas with higher pre-vaccine infection rates had more to gain with the introduction of the vaccine. If children that would otherwise have contracted measles miss fewer days of school after the vaccine is introduced, then areas with comparatively high incidence of measles pre-vaccine introduction will experience a larger gain in human capital accumulation as a result of the vaccine campaign.

Consistent with these expectations, I observe gains in health and education following the introduction of the measles vaccine, with greater gains for areas with a higher initial measles incidence rate. Not only do children benefit from not getting the measles, but they also experience a protective effect from the measles vaccine. Since children no longer experience the weakened immune effects from measles that increase their susceptibility to other childhood infectious disease for up to four years, children are in better overall health post-vaccine introduction. These gains in childhood health translate into increases in school enrollment of 0.3 percentage points and full-time school attendance of 0.2 percentage points in the short-run and 3% higher earnings in the long-run.