I do think this is an appropriate counter-example, but I’m curious how much modern medicine would change the impact (and preserve the case for optimism).
Rapid vaccine development does indeed give some cause for optimism. Some counters that I'd have to that would be a potential resurgence of polio in the US [1] and the appearance of drug-resistant pathogens (typhoid fever in this case) [2], just to keep us on our toes and curb our enthusiasm...
