Performance of Zoster Vaccine Live (Zostavax): A Systematic Review of 12 years of Experimental and Observational Evidence

BACKGROUND: One in three people in the U.S. will develop herpes zoster during their life. Zoster Vaccine Live (ZVL or Zostavax™), has been licensed in the U.S. since 2006 to prevent herpes zoster. ZVL protection has been shown to wane with time and estimates of effect can be imprecise. We performed a systematic review of the duration of efficacy and effectiveness of ZVL against herpes zoster (HZ). METHODS: We systematically searched PubMed, Embase, Cochrane, and clinicaltrials.gov for vaccine efficacy or effectiveness (VE) studies of ZVL. Two authors independently screened each title and abstract, and potential VE studies were reviewed in-depth. Eligibility criteria included original data on ZVL prevention of HZ in a general population of immunocompetent recipients ≤ 60 years old. Selected articles were abstracted, independently reviewed, and discrepancies adjudicated. We attempted to locate relevant unpublished work and contacted authors for additional data, where necessary. Measures of association were illustrated on a forest plot and converted to VE (1-hazard ratio or risk ratio or odds ratio). RESULTS: We screened 1302 articles; 17 underwent full text review and 8 met inclusion criteria and were abstracted for this review. Selected studies included 1 phase III randomized controlled trial, 2 quasi experimental and 5 observational studies. One experimental and 5 observational studies estimated VE during the period from vaccination up to 4 years following vaccination; estimates across studies ranged from 33%-55%. Two quasi experimental and 3 observational studies estimated VE for ≥ 4 years following vaccination; estimates ranged from 19%-40%; the median estimate was 24% (Figure). Pooled VE was not calculated due to heterogeneity in length of follow up, age distribution of study subjects, as well as adjustment for factors such as underlying medical conditions. CONCLUSION: Most experimental and observational studies estimate VE just above 50% during the 3 years following receipt of ZVL. Beyond 3 years, ZVL protection wanes, with most studies estimating a VE of ≤24% after 4 years. Information on overall efficacy and duration of protection from ZVL will guide policy decisions regarding its use. DISCLOSURES: E. Belongia, Novavax: Investigator, Research support