Varicella Vaccine Effectiveness and Duration of Protection: A Systematic Review and Meta-Analysis

Background: This study provides a comprehensive review of studies comparing the effectiveness of varicella vaccinations and the duration of their protection. Methods: We conducted a systematic literature review to identify comparative studies evaluating the effectiveness of the varicella vaccine. A meta-analysis was performed to assess the effectiveness of one-dose and two-dose vaccinations, as well as the outcomes for moderate and severe illness, and the duration of protection, using random effects models. Results: Out of 66 studies, 57 reported the effectiveness of a single-dose varicella vaccine, 28 examined the two-dose vaccination, and 25 focused on effectiveness against moderate to severe disease. Of these, 59 were observational studies and 7 were trials. Thirteen studies reported the duration of protection. The overall vaccine effectiveness for a single dose was 79% (76–82%; I² = 97.2%), while for two doses, it was 94% (93–96%; I² = 90.8%). The overall effectiveness against moderate or severe illness was 92% (90–94%; I² = 90.3%). The duration of protection showed a slight decline over time. Evidence suggests that both one and two doses of the varicella vaccine offer short-term protection, though this protection wanes rapidly. Conclusion: The two-dose vaccination demonstrated superior clinical efficacy compared to the one-dose vaccination, with protection slightly diminishing over time. These findings highlight the importance of implementing universal two-dose varicella vaccination programs in countries.