- 📜 NEW WORKING PAPER 📜 What was the true case fatality rate (CFR) of smallpox? My new paper with Romola Davenport (Cambridge) revisits this question using 18th-century data from Sweden and Iceland—and challenges the long-held belief that smallpox CFRs were 20–30%. 🧵👇 1/6May 13, 2025 19:25
- Using high-quality mortality records, we estimate smallpox CFRs in two very different contexts: 📍 18th-century Sweden (endemic smallpox): CFR ~8–10% 📍 1707-9 Iceland smallpox epidemic: CFR ~40–53% 2/6
- Why the such different CFRs? In endemic settings like Sweden, smallpox was a childhood disease and adults very rarely contracted smallpox. But in Iceland, the epidemic struck a population where both adults and children were susceptible. This raised the CFR dramatically. 3/6
- Our findings suggest that smallpox’s lethality wasn’t just about the virus—it was about context. When adults and children were sick together, there was no one to fetch water, cook food or nurse the sick. High CFRs often reflect crisis conditions, not just the innate virulence of the pathogen. 4/6
- So why is the consensus CFR (20-30%) for endemic smallpox too high? Three factors likely biased estimates of CFRs upwards: 1) Under-reporting of smallpox cases 2) Positive selection into vaccination after 1796 3) Selection of severe smallpox cases into hospital samples used to estimate CFRs 5/6
- 🚨 Bottom line: The oft-cited 20–30% CFR for Variola major doesn't hold up across time and place. We argue for a more nuanced, historically grounded view—context matters. 📄 Read the full paper here: www.lse.ac.uk/Economic-His... 6/6
