When Diseases Return from the Epidemiological Honeymoon: The Reemergence of Smallpox in 19th Century Germany and its Lessons for Public Health Policies after COVID-19

The COVID-19 pandemic has overwhelmed public health systems around the world. At the same time, misinformation about vaccines spread with unprecedented speed. Governments and international organizations are currently evaluating strategies for future outbreaks of infectious diseases. This paper provides historical evidence about the last large-scale smallpox epidemic that ravaged Germany in 1870 to 1872. The health authorities of the different German states faced almost the same problems as their 21st century counterparts: Mounting pressure from anti-vaccination groups and increasing mobility and demographic change that facilitated the spread of pathogens. Using both qualitative sources and statistical evidence, the paper shows that the 1870 to 1872 outbreak was mostly due to incomplete vaccination uptake and the corresponding accumulation of susceptible individuals. This phenomenon – also referred to as a post-honeymoon-epidemic – was dramatically exacerbated because smallpox incidence shifted from very young age-groups to highly mobile adolescents and adults. The main conclusion from this historic German experience is that a rise in vaccine hesitancy requires resolute and sustained public health responses.