Measles in Minsk, Belarus, 2001-2003: clinical, virological and serological parameters.

Background: A number of cases of measles have been reported in the Republic of Belarus despite vaccine coverage of 98%. The absence of information on measles virus genotypes circulating in the Republic of Belarus has made it difficult to asses the situation.

Objectives: The purpose of this study was to isolate and sequence measles virus strains from clinical cases in Minsk, Belarus, and to estimate the role of vaccine failure in those cases.

Study Design: Between 2001 and 2003 years, 14 measles cases admitted to the Hospital of Infectious Diseases of Minsk were enrolled in our study. Clinical, routine laboratory, as well as serological and virological examinations were carried out. Detection of measles antibodies and IgG avidity testing was performed using commercial test kits. All measles cases were confirmed by RT-PCR and phylogenetically characterized.

Results: Only 42.9% of the cases met the WHO laboratory criteria for measles, however, all cases were confirmed by RT-PCR. Most of the measles cases were attributed to secondary vaccine failure (SVF). Phylogenetic analysis revealed the presence of genotype A virus strains in 2001 and 2002 with D6 and D7 genotypes in 2003.

Conclusions: For the first time, MVs were genetically characterized in Belarus. Our results suggest that in a highly vaccinated population, most of measles cases represent vaccine failures and are vaccine-modified. Our results also indicate that confirmation of a clinical diagnosis of vaccine-modified measles requires a combination of serological and virological tests.