Germs in the Family: The Long-Term Consequences of Intra-Household Endemic Respiratory Disease Spread
While the COVID-19 pandemic has laid bare the large costs of infectious diseases, less attention has been paid to the impacts of more common, endemic respiratory viruses that frequently circulate in the population, especially when it comes to their potential long-term consequences for population health, human capital, and economic outcomes. This paper uses Danish population-level administrative data on 35 birth cohorts of children to provide a comprehensive analysis of both the mechanisms through which infants become infected by respiratory illnesses, as well as the consequences of early-life respiratory disease exposure for their later outcomes. First, we document a striking difference in the likelihood of severe respiratory illness by birth order: younger siblings have two to three times higher rates of hospitalization for respiratory conditions before age one than older siblings at the same age. We argue that the family unit is central in virus transmission, with older children "bringing home" the virus to their younger siblings. We then combine the birth order variation with within-municipality variation in respiratory disease prevalence among preschool-aged children to identify differential long-term impacts of early-life respiratory illness between younger and older siblings. We find that moving from the 25th to the 75th percentile in the local disease prevalence distribution ("disease index") is associated with a 30.9 percent differential increase in the number of respiratory illness hospitalizations in the first year of life for younger compared to older siblings. In the long term, for younger relative to older siblings, we find a 0.5 percent differential reduction in the likelihood of high school graduation, and a 1.3 percent additional reduction in age-30 earnings.
We thank Jon Guryan, and conference and seminar participants at the Barcelona Graduate School of Economics Summer Forum, the 2021 American Society of Health Economists annual meeting, the 2021 European Economic Association meeting, the 77th Annual Congress of the International Institute of Public Finance, the Ca’Foscari University of Venice, University of Milan, Universita Cattolica, UC Irvine, and VATT Institute for Economic Research Helsinki for helpful comments. The views expressed herein are those of the authors and do not necessarily reflect the views of the National Bureau of Economic Research.