THE PROBLEM OF PERTUSSIS IN SOME GEOGRAPHIC REGIONS OF THE WORLD

Pertussis infection remains a high-priority issue both for Russian health care and abroad. A rise of pertussis incidence in various human age groups instigates a search for new ways to fight this infection and improve methods for its laboratory diagnostics. By taking into consideration a short-term effect induced by acellular and whole-cell vaccines, a feasibility of introducing the second or even the third pertussis revaccination is vigorously debated. Objective of the study was to analyze the experience and effectiveness of acellular pertussis vaccines in countries, which use the second and third pertussis revaccination in the National Immunization Schedule in order to have an insight into adjusting strategy and tactics of pertussis immunization in Russia. Analyzing pertussis prevalence demonstrated that despite a wide immunization coverage pertussis incidence in the last years (2008-2015) was increased in a large number of countries in the European region, as well as in Australia, Canada and USA. However, the reasons for elevated pertussis incidence have not been clarified yet. On one hand, it may be accounted for by low vaccination coverage in adolescents and adults; weakened immune protection after vaccination; genetic changes in Bordetella pertussis; shortened durability of protective immunity in children vaccinated with acellular vs. whole-cell vaccine; improved monitoring and morbidity reporting, as well as improved laboratory diagnostics due to shifting from serological and bacteriological to molecular genetic assays. In an attempt to solve this issue, researchers from several countries collaborate to discuss and develop a strategy to reduce pertussis incidence. For Russia, the most important is to empower and/or improve existing infant immunization strategy in order to provide wide coverage with the four dose pertussis vaccine for decreasing the risk of pertussis morbidity and mortality. It is worth noting the "cocoon" strategy given the high risk of pertussis infection in children of the first months of life. We believe that for Russia it is worth investigating an opportunity of using children 2-3 months of life an acellular vaccine as the first vaccination, which is expected to increase the coverage of this cohort and allow to increase proportion of children who might complete vaccination by 5 months of age. At the same time, more reasonable might be to preserve a number of age groups for pertussis vaccination in the current National Immunization Schedule, as expanding age limits for vaccination might put a risk at increasing pertussis morbidity in older individuals, which could be hard to diagnose.