They were testing a vaccine to prevent hookworm infection. [0] After giving the experimental vaccine, they intentionally inoculated the research subjects with hookworms to measure whether the vaccine prevented hookworm infection.
Yes. While today, the more common meaning of the word is "to introduce immunologically active material (such as an antibody or antigen) into especially in order to treat or prevent a disease", an older but still used meaning is "to introduce a microorganism into".