[Anti-pertussis immunity in children in the cities of Northwestern Federal District with various population].

AIM: Evaluate the state of immunity against pertussis in children living in St. Petersburg and regional centers of Northwestern Federal District (NFD). MATERIALS AND METHODS: The level of anti-pertussis antibodies by EIA and agglutinin reaction (AR) was studied in 419 children living in St. Petersburg and by AR in 239 children living in regional centers of NFD. Blood sera in AR were studied by using liquid pertussis diagnosticum (Biomed, Russia). RESULTS: In St. Petersburg the frequency of detection of high level of antibodies was the highest in the 15 - 17 age group that indicates a high level of latent morbidity in grownups. The frequency of detection of high level of antibodies in the 3 - 4 and 9 - 10 age groups in regional centers was significantly lower, and the fraction of sera with undetected level of antibodies--significantly higher compared with St. Petersburg, that gives evidence on low circulation of causative agent, lack of "epidemizing" of children in small cities. CONCLUSION: The question of introduction of second revaccination against pertussis in children at the age of 6 is actual, because one vaccination is not enough for prolonged sustaining of population immunity intensity.