San Franciscans were understandably skeptical of vaccines in the 1860s, even when a deadly wave of smallpox swept through The City.

Some vaccines consisted of harvesting ground-up scabs from smallpox-infected patients to induce a mild — and hopefully inoculating — case. Many doctors urged patients to get injected with a virus extracted from cows, which was not contagious and not lethal in humans, but seemed to provide immunity from smallpox. It is from the Latin word for cow — vacca — that the name vaccine is derived.

Others speculated that the foggy environment might diminish vaccines’ effectiveness.

But the 19th century was a time of remarkable medical advances. Scientists were just beginning to make the connection between germs and disease. Sterilization and anesthetics were being in

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