Ralph Lawton received the 2025 Dorothy S. Thomas Award for his winning paper, titled “Early Life Infectious Disease Exposure – The Hygiene Hypothesis and Lifespan Evidence From Hookworm.” He made extensive and creative use of data, with direct implications for today. With over 400 million people globally living with hookworm, his paper shows evidence for the long-term consequences of childhood deworming programs.
Abstract
Exposure to infectious disease in early life may have long-term ramifications for health and lifespan. However, reducing pathogen exposure may not be uniformly beneficial. The rise of modern sanitation and reduction of infectious diseases has been implicated in increasing levels of allergy and immune dysregulation: termed, the "hygiene hypothesis." This study leverages quasi-experimental variation from combining pre-campaign hookworm exposure with the Rockefeller Sanitary Commission’s de-worming campaign in the early 20th century to rigorously examine the impacts of childhood hookworm exposure on adult lifespan and morbidity. Findings show de-worming before age five leads to 2.5 additional months of life in a large sample of adult death records. Further, decreasing hookworm exposure is related to improvements in biomarkers for inflammation and skin-tested allergies, in contrast to predictions of the “hygiene hypothesis”. Placebo tests using health outcomes that should not be affected by de-worming do not show similar patterns. Findings provide new, rigorous evidence of the role of early life infectious disease on later life health outcomes, and the mechanisms through which it occurs. Overall, childhood de-worming leads to improvements in morbidity and lifespan decades later. View paper.