ALB and chickenpox: The varicella vaccine without HSA was non-inferior to the licensed vaccine in terms of anti-VZV antibody Geometric Mean Titre/Concentration ratio (1.12 [95 % CI:0.86–1.46] by IFA; 1.12 [95 % CI:0.93–1.33] by ELISA) approximately six weeks after the first dose of the 2-dose vaccination course.