Non-Pharmaceutical Interventions and Mortality in U.S. Cities during the Great Influenza Pandemic, 1918-1919

Non-pharmaceutical interventions (NPIs) were measured by Markel, et al. (2007) for U.S. cities during the second wave of the Great Influenza Pandemic, September 1918-February 1919.  The NPIs were in three categories: school closings, prohibitions on public gatherings, and quarantine/isolation.  An increase in NPIs sharply reduced the ratio of peak to average deaths, with a larger effect when NPIs were treated as endogenous.  However, the estimated effect on overall deaths was small and statistically insignificant.  The likely reason that the NPIs were not more successful in curtailing mortality is that the interventions had a mean duration of only around one month.