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Aim: Analysis of results of virological study of material from children of migrants and evaluation of intensity of immunity against polioviruses in these children., Materials and Methods: 1668 feces samples from patients with acute flaccid paralysis and contact individuals and 479 feces samples from healthy children from families of migrants, as well as 1012 blood sera of children aged 3 - 4 and 14 - 15 years living in the same territory of Russia, and 169 blood sera of children of migrants were studied. Polioviruses and non-polio enteroviruses were isolated by standard procedures recommended by WHO in 3 cell cultures - RD, L20B and Hep-2. Virus identification was carried out by microneutralization test with rabbit antisera against poliomyelitisvirus, RIVM (Bilthoven, Netherlands). For intra-type differentiation EIA and PCRwere used. Antibody titers were determined in microneutralization reaction with reference poliovirus vaccines strains in Hep-2 cell culture., Results: The frequency of detection of polioviruses in children of migrants was significantly higher than in patients with acute flaccid paralysis. In a larger percent of cases children of migrants did not have protective antibody titers against polioviruses of all the 3 serotypes., Conclusion: Migrants as a significant source of poliovirus detection may be an indicator group for detection of signs of unfavorable epidemic situation. Based on the results of epidemiologic surveillance of migrants the fact of import of wild poliovirus into North-West of Russia with the absence of poliomyelitis was proven, which confirms an important role of this form of monitoring in the system of poliomyelitis control.

Immunization schedules implemented in various countries by using poliovirus vaccines are presented. Approaches to prevent development of vaccine associated paralytic poliomyelitis and risk groups for this infection are discussed. In recent years poliomyelitis morbidity situation in the European region has become more complex, with the example of poliomyelitis outbreak in Tajikistan in 2010. The resulting problem of protection of Russian against emergence and spread of poliomyelitis caused by wild type virus is discussed.

The modern view of the role of enteroviruses in the eradication of poliomyelitis is presented. Enteroviruses were discovered in the XX century. In the 1950s they caused great epidemics of poliomyelitis and serous meningitis in many countries of the world. The introduction of oral poliomyelitis vaccine (OPV) into medical practice made it possible to eliminate the epidemics of poliomyelitis in a short time. Poliomyelitis morbidity was reduced to sporadic cases and in a number of regions disappeared. OPV produced non-specific influence also on the epidemics of serous meningitis, as well as on a case incidence. The eradication of poliomyelitis viruses and the cessation of immunization with OPV will not result in eradication of paralytic diseases. Paralytogenic viruses of 20 serotypes circulate in nature, and some of these viruses are capable of causing the outbreaks of severe paralytic diseases. The authors propose either to retain immunization with OVP as tour immunizations with monovaccine of type 2, or to create new live enterovirus vaccines on the basis of avirulent enterovirus strains.

The paper presents data on the design and practical medical use of vaccines for the prevention of urgent viral infections, including those against poliomyelitis (oral poliomyelitis vaccine), tick-borne encephalitis, hepatitis A, rabies, and enteroviris 71. It shows the basic lines in the improvement of manufacture and biological control of vaccines and in the development of a new vaccine for prevention of hemorrhagic fever with the renal syndrome.

An essential reduction in the incidence rate of six infantile infections within the Expanded Immunization Program was accompanied by occurrence of new problems in vaccine prophylaxis. 1. Vaccine-dependence--the reoccurrence of vaccine-prevented infections in those cases when vaccination was stopped. 2. A choice of strategy in the immune prophylaxis of poliomyelitis during the post-liquidation period bearing in mind the elimination of vaccine strains from the human population and a possible global refusal from vaccination. 3. Elaboration of regional programs for eliminating the measles in big territories. 4. Alteration of protective antigens Bordotella pertussis. The relationship of such alterations correlates with a rise in the Bordotella pertussis incidence rate with regard for multiple comprehensive vaccinations in the USA and Western Europe.

The frequency of vaccine poliovirus isolation from children aged under 3 years was studied in Belarus, a country with a high level of immunization against poliomyelitis. Antigenic and genetic characteristics of the isolated strains were studied. Vaccine poliovirus detection rate was high (11.8%). Polioviruses were isolated from children immunized recently (27.2%), immunized more than 2 months before (7.5%), and from non-immunized children (9.8%). An appreciable number (36.1%) of the isolated strains were antigenically and/or genetically modified derivatives of Sabin virus. Epidemiological data and genetic characteristics of the isolated polioviruses indicate that some of them can be sufficiently transmissive for maintaining their "silent" circulation even in a population with a high level of immunization.