Systematic Review of Effectiveness of Varicella Vaccines: A Critical Appraisal: Immunization Experts Viewpoint.

In this systematic review and descriptive meta-analysis, the authors examined the post-licensure estimates of varicella vaccine effectiveness (VE) among healthy children. Publications that reported original data on dosespecific varicella VE among immunocompetent children were included. Random effects meta-analysis models were used to obtain pooled one dose VE estimates by disease severity (all varicella and moderate/severe varicella). Within each severity category, pooled VE by vaccine and by study design were assessed. The pooled 1dose VE was 81% (95% CI 78%, 84%) against all varicella and 98% (95% CI 97%, 99%) against moderate/ severe varicella with no significant association between VE and vaccine type or study design. For 1-dose, median VE for prevention of severe disease was 100% (mean 99.4%). The pooled 2-dose VE against all varicella was 92% (95% CI 88%, 95%), with similar estimates by study design. The authors conclude that one dose of varicella vaccine was moderately effective in preventing all varicella, and highly effective in preventing moderate/ severe varicella, with no differences by vaccine. The second dose adds improved protection against all varicella.