Methods: An extensive literature search was performed in Embase and Medline for the period January 2007 to January 2018 to identify peer-reviewed, original, English study manuscripts reporting the results of observational studies of ZVL VE. In all studies, HZ cases were identified from HZ diagnosis codes, with only two studies also requiring HZ-specific antiviral use. For PHN, different case definitions were used across studies, usually without validation from medical chart review.
Results: Seven original effectiveness studies were identified (5 from the United States and 1 each from the United Kingdom and Canada) that assessed HZ effectiveness in the general population. Five of these studies also assessed PHN effectiveness. Vaccine effectiveness to prevent HZ was similar across studies in the early years following vaccination, but tended to diverge in the later years (overall VE against HZ ranged from 33% to 62%, clustering around ~50% across studies providing this information). Overall VE against PHN ranged from 55% to 88%, clustering around ~65%.
Conclusion: Real-world observational studies assessing the effectiveness of ZVL in preventing HZ and PHN in the general population reported generally similar results. Differences in VE estimates across studies were likely driven by differences in study design and methods, including sample size and age of study population, HZ and PHN case definition, duration of follow-up, and methods of covariate selection, definition and adjustment. We are currently conducting a meta-analysis to identify and quantify the potential heterogeneity across studies and calculate summary VE estimates.
Merck and Co. Inc.:
S. Calhoun, Merck and Co. Inc.: Employee , Salary .
K. Johnson, Merck & Co., Inc.: Employee , Salary .
Y. Moride, Merck: Research Contractor , Consulting fee .