Virology USMLE Step 1 Practice Question
A 67-year-old man with hypertension presents with fever (38.5°C), cough, and myalgias for 3 days despite receiving the influenza vaccine 2 months ago. Vital signs show HR 98/min, BP 142/88 mmHg, RR 22/min, SpO2 98% on room air. Rapid influenza test is positive. He denies recent sick contacts. He takes lisinopril daily. Which mechanism best explains incomplete protection against this seasonal influenza strain despite prior vaccination?
Answer choices
- ALatency within dorsal root ganglia
- BIntegration of viral DNA into the host genome
- CAntigenic variation of bacterial pili
- DReassortment of segmented viral genomes between human and animal strains
- EPoint mutations in viral genes encoding hemagglutinin and neuraminidaseCorrect answer
- FFailure of the vaccine to stimulate a CD8+ T cell-mediated immune response
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