During the last decade shift in incidence of pertussis toward the older age groups was observed. Also marked increase in incidence of pertussis in the second half of 1997 and first half of 1998 has occurred in our highly vaccinated population. In lieu of those facts question arises on effectiveness of national vaccination program in respect to immunological adequacy of vaccine used as well as to the vaccinations calendar. Estimations of the values of vaccine efficiency coefficient were calculated for age groups of 2-5, 6-9 and 10-13 years for six month periods in 1997-1998. Sustained good effectiveness of vaccinations was observed in a group 2-5 years of age. In older groups marked decrease of effectiveness was observed during 1997/1998 outbreak of whooping cough. The effectiveness of vaccinations among children of 10-13 years dropped at the outbreak to insignificant levels. Such results indicate good vaccine protection at the age of 2-5 which reflects immunological adequacy of vaccine used in Poland. But this protective effect declines in later years indicating need for additional dose of vaccine for children after five years of age.