 On May 19, 1924, Spencer put a large dose of mashed wood ticks, from lot 2351B, and some weak carbolic acid into his arm by injection.This vaccine worked, and for some years after it was used by people in that region to convert the illness from one with high fatality rate (albeit low incidence) to one that could be either prevented entirely (for many of them) or modified to a non-deadly form (for the rest).Today there is no commercially available vaccine for RMSF because, unlike in the 1920s when Spencer and colleagues developed one, antibiotics are now available to treat the disease, so prevention by vaccination is no longer the sole defense against likely death.