A 0.1% case fatality rate sounds small until you apply it to a virus that infected essentially every child born. Pre-vaccine, that meant 400-500 deaths per year in the U.S. and over 2 million deaths annually worldwide. But death isn’t the only outcome that matters. In the U.S. every year, measles caused 48,000 hospitalizations, 4,000 cases of encephalitis (a quarter of whom were left permanently brain damaged or deaf), and 7,000 seizures. Then there’s immune amnesia, which leaves kids vulnerable to other infections for years, and SSPE, a fatal brain disease that can appear a decade after recovery. “99.9% survival” isn’t the flex you think it is. The vaccine doesn’t just prevent death. It prevents hospitalization, brain damage, deafness, and years of immune vulnerability. Reducing all of that to “not the plague” is missing the point entirely.

Aaron Siri says no one has identified errors in his ACIP presentation. Here are several, with citations to the primary literature. 🧵