This bottle of Rocky Mountain spotted fever vaccine from the early 1940s represents much scientific work and practical experimentation. There were no strict research protocols for vaccine development and testing in the early 19th century. There was no oversight or approvals from the Food and Drug Administration. The Hygienic Laboratory (NIH’s precursor) had regulatory authority, testing commercial vaccines for safety and effectiveness. Spencer worked at the Hygienic Laboratory and was certainly familiar with the tests required to prove that a vaccine worked safely and at what dose it should be given, as well as the standards for producing a safe vaccine. He knew proving that his RMSF vaccine worked would take more than inoculating himself with it.
After experimenting with different combinations of fed vs. unfed ticks and ticks in different stages of their life cycle to get the highest concentration of RMSF in the vaccine, Spencer and Parker were ready for the next step. In February 1925, they conducted an experiment in 18 monkeys to see if the vaccine was effective and safe. None of the vaccinated monkeys died; all of the unvaccinated monkeys did.
Next was to test the vaccine on people, and the Canyon Creek Schoolhouse laboratory staff became the participants in this early clinical trial. Thirty-four laboratory and field workers were vaccinated, and none had a severe reaction.
There were questions about the vaccine: what was the optimum dose? How long did immunity last? And how long did it take to gain immunity after being vaccinated? That last question was answered in April 1925, when a cattle-dipper for Montana State Board of Entomology was vaccinated. He came down with RMSF a few days later but recovered. Four other people in the Bitterroot Valley who also got RMSF at the same time, but had not been vaccinated yet, all died. From this unplanned experience, Spencer and Parker learned the time required to gain immunity after vaccination: 10 days.
