The purpose of this study is to evaluate the immunogenicity, safety and influence of the delivery system (needle-free injector or syringe with needle) of fractional doses (dose sparing) (23,3 and 43,3 PFU - plaque-forming units - of live attenuated OKA strain of Varicella-zoster virus and 100 radioimmunoassay units HAV) of chickenpox and Hepatitis A ( vaccines, intradermally administered, compared with full dose of 103,3 PFU, subcutaneously administered, in 600 primo (first) vaccinated children aged 13 to 30 months selected at random at day care centers in São Paulo. Vaccines will be tested sequentially (Varicella on day 0 and Hepatitis A on day 45). Only 400 children will be randomized again for Hepatitis A vaccine testing, the remaining 200 children will receive the regular dose of Hepatitis A vaccine without further assessment. Doses will be administered using two systems: Disposable Needle-free Syringe Jet Injector (DSJI), compared with the conventional procedure using syringes and needles. Serial blood samples will be blindly analyzed to detect antibody seroconversion. Local and systemic adverse events will be assessed according to definition established by Brighton Collaboration Group, 24 and 72 hours, 7 days, 14 days, 21 days and 45 days after each vaccination, through clinical evaluation and telephone calls.