Pertussis in Poland.
Since 1997, an unexpected 2-5-fold increase in the incidence of pertussis has been reported in Poland in comparison with the previous 10 years, although the introduction of the diphtheria-tetanus-pertussis (DTP) vaccination in 1960 reduced the incidence of pertussis approximately 100-fold in the 1980s. The aim of the study was to analyse all available data on pertussis in Poland to identify the risks associated with its re-emergence. Available data on notification, incidence, mortality, hospitalization, geographical distribution, incidence according to age, and diagnosis of pertussis were collected from national surveillance monographs and statistically evaluated. Analyses performed in the study found two periods of rising and falling trends: in the incidence before and after 1989, respectively. Moreover, after 1989, the age-specific incidence among children aged 0-4 years decreased, and among 5-9, 10-14, and 15-19 year olds increased in comparison to the previous decade. The incidence rate of pertussis among infants was similar in both decades analysed. Clustering of pertussis incidence increase in provinces along a line from North East to South West was observed. As vaccination coverage did not decrease and diagnostics have not been improved since the 1980s, it is possible that waning immunity and the appearance of Bordetella pertussis vaccine escape mutants are involved in the changing pertussis epidemiological parameters. Further monitoring studies, together with improving diagnostics, might allow more precise epidemiological data to be obtained. An additional booster dose of acellular pertussis vaccine at age 6 years has been included in the current vaccination schedule.