Background: In Turkey, several changes have been made in the vaccination schedule. Vaccines against diphtheria, tetanus, pertussis and poliomiyelitis were applied as DTwP and OPV until the end of 2006. Hib vaccine was added to the schedule and was administered as a separate injection in 2007 as DPT + OPV + Hib. DTaP-IPV/Hib combined vaccine replaced them in 2008. The aim of this study was to evaluate the alterations in the frequency of adverse reactions of these different schedules in the consecutive three years.