An observational time-motion study investigated logistic, programmatic and safety-related advantages and limits in the delivery of a fully liquid DTP-HepB-Hib combination vaccine versus a lyophilized combination vaccine requiring reconstitution. The study was conducted in 2006, observing 312 child vaccinations in a tertiary hospital setting in Kolkata, India. The time for vaccination was on average 46s (35.12%) lower with the fully liquid vaccine (p<0.05). In addition, the fully liquid combination was easier and potentially safer to handle and as well tolerated as the lyophilized formulation. Fully liquid combination vaccines have the potential to simplify immunization schedules, contribute to better resource management and improve efficiency of immunization programs.