ABSTRACT
The results of virologic testing of clinical materials and epidemiological analysis of vaccine-associated paralytic poliomyelitis (VAPP) cases obtained in 2006-2013 during AFP surveillance are presented. Among the 2976 cases of AFP 30 cases were VAPP. 15 cases were observed in OPV recipients, whereas 15 cases were observed in non-vaccinated contacts. The age of the patients varied from 4 months to 5.5 years (13.6 ± 12.4 months old). Children younger than 1 year constituted 63.3% of the group; boys were dominant (73.3%); 53.3% of children were vaccinated with OPV; the time period between receipt of OPV and onset of palsy was from 2 to 32 days (18.7 ± 8.2). Lower paraparesis was documented in 48.3% of patients; lower monoparesis in 37.9%; upper monoparesis, in 6.9%; tetraparesis with bulbar syndrome, in 6%. The majority of the patients (85.7%) had an unfavorable premorbid status. The violations of the humoral immunity were found in 73.9% cases: CVID (52.9%), hypogammaglobulinemia (41.2%); selective lgA deflciency (5.9%). In 70.6% cases damage to humoral immunity was combined with poor premorbid status. The most frequently observed (76%, p < 0.05) represented the single type of poliovirus--type 2 (44%) and type 3 (32%). All strains were of the vaccine origin, the divergence from the homotypic Sabin strains fell within the region of the gene encoding VPI protein, which did not exceed 0.5% of nucleotide substitutions except vaccine derived poliovirus type 2--multiple recombinant (type 2/type 3/ type 2/type 1) with the degree of the divergence of 1.44% isolated from 6-month old unvaccinated child (RUS08063034001). The frequency of the VAPP cases was a total of 1 case per 3.4 million doses of distributed OPV in 2006-2013; 2.2 cases per 1 million of newborns were observed. This frequency decreased after the introduction of the sequential scheme of vaccination (IPV, OPV) in 2008-2013 as compared with the period of exclusive use of OPV in 2006-2007: 1 case per 4.9 million doses, 1.4 cases per million newborns and 1 case per 1.9 million doses, 4.9 cases per 1 million newborns, respectively. The study has been financed from Russian Federation budget within the framework of the Program for eradication of poliomyelitis in the Russian Federation, WHO Polio eradication initiative, WHO's European Regional Bureau, Russian Foundation for Basic Research (project No. 15-15-00147).
