One or two doses of live varicella virus-containing vaccines: Efficacy, persistence of immune responses, and safety six years after administration in healthy children during their second year of life.

•The study compared efficacy of one or two doses of varicella vaccines versus a control group.•We present efficacy results up to six years post-vaccination.•Efficacy of two MMRV doses or one varicella vaccine dose persists six years post-vaccination.•Two doses of MMRV were highly efficacious against varicella of any severity.•One dose of varicella vaccine was highly efficacious against moderate and severe disease.