EPIDEMIC PROCESS OF RUBELLA DURING MASS VACCINATION OF CHILDREN

Aim. To reveal features of rubella epidemic process during start of mass immunization and to determine rubella virus genotypes circulating in Saint-Petersburg. Materials and methods. Official data on rubella morbidity during 1995 — 2007 and number of vaccinated against rubella children and adults were used in this study. During 2006 — 2008 males aged 17 — 20 years with rubella diagnosis were eligible for laboratory test on rubella. Nasopharyngeal swabs and blood specimens were tested by PCR and virus isolation on cell culture (PK13). Genotyping of isolates was performed on the basis of 600 nucleotide sequence of E1 gene from 8731 to 9653 n.p. Results. It was shown that mass vaccination of children and young women against rubella during 4 years resulted in 3-fold drop of rubella incidence in whole population, which diminishes the probability of infection in pregnant women and born of children with congenital rubella syndrome. In age structure of rubella morbidity the proportion of children aged 3 — 6 and 7 — 14 years decreased by 1.5-fold. Epidemic process loss the features of autoregulating system (periodicity and seasonal incidence peaks). Results of genotyping showed that isolates belonged to genotype 1E. High degree of homology (97.7 — 99,6%) to isolates from Barnaul and Belorussia was demonstrated. Conclusion. Issues on isolates’ origin and success of measures on elimination of endemic rubella could be resolved by further studies on isolation and genotyping of rubella virus strains in Saint-Petersburg and North-East region of Russian Federation in the whole.

rubella, epidemic process, vaccination, viral genotypes, phylogenetic analysis