In Reply: Drs Rothberg and Smith correctly point out a decline in vaccine efficacy during the first year in the SPS.1 Consequently, the shorter follow-up time in our study might have resulted in an underestimate of the incidence rate in the vaccinated group. In fact, had follow-up time in SPS been curtailed to the 1.7 years in our study, the estimated efficacy would have been 55%, exactly what we observed.2
Tseng HF, Jacobsen SJ. Herpes Zoster Vaccine and Older Adults—Reply. JAMA. 2011;305(14):1410–1411. doi:10.1001/jama.2011.423
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