Epidemiology & Prevention USMLE Step 1 Practice Question
A 7-year-old boy with acute lymphoblastic leukemia currently receiving chemotherapy (HR 102, BP 98/62, temp 37.2°C) has an absolute neutrophil count of 800/μL and cannot receive live vaccines due to immunosuppression. His pediatrician emphasizes that high vaccination coverage among classmates is especially important for protecting him from measles exposure, despite normal measles serology. Which of the following best explains this protective effect?
Answer choices
- ACross-reactive immunity
- BTertiary prevention
- CPassive immunity
- DArtificial active immunity
- EHerd immunityCorrect answer
- FInnate immune recognition of measles antigen
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.