[Laboratory diagnostics and monitoring of virus circulation in surveillance system for rubella in Belarus].

AIM: To summarize data on laboratory diagnostics of prenatal and postnatal rubella and molecular monitoring of rubella virus circulation in Belarus obtained during implementation of rubella elimination program. MATERIALS AND METHODS: Serum samples from 2314 persons were tested on the presence of IgM to rubella virus and measles virus (in case of negative result on rubella) using respective enzyme immunoassays. Virological testing using RT-PCR as well as genotyping on the basis of E1 gene fragment sequencing were also performed. Two viruses isolated in Belarus were set as reference strains of genotypes 1G and 1h. RESULTS: Implementation of laboratory diagnostics allowed to differentiate cases of rubella from other exanthematous infections, significantly increase the number of laboratory-confirmed cases among all reported cases, and show presence of endemic circulation of rubella virus strains of 3 different genotypes (1G, 1E, and 1h) in Belarus (2004-2006). In 2006, when relatively high incidence of rubella was reported in the country (24.39 per 100,000 population), the risk of congenital rubella syndrome was not less than 9 per 100,000 births. Conducted in October 2005-May 2006 additional rounds of immunization against rubella (>1 million people were vaccinated) decreased incidence to single cases. CONCLUSION: Obtained data show achievability of indigenous rubella elemination by 2010. Revealed genetic diversity of rubella virus strains allowed to update the International classification of wild rubella viruses.

[Surveillance of acute flaccid paralysis in Belarus].

The ten-years experience of acute flaccid paralysis (AFP) surveillance in Belarus has been summarized. Among 456 AFP cases reported from 1996 to 2005, 11 were classified as vaccine-associated paralytic poliomyelitis (VAPP), 445--as non-polio AFP. The risk of VAPP for the period 1996-2001 was 1 case per 745,000 used doses of oral poliovaccine (OPV). For the recipients of OPV the risk was 1 case per 911,700 doses and for the first-dose recipients--1 case per 96,000 doses. The high incidence of VAPP was a reason for implementation of sequential polio vaccination schedule in 2000. Guillain-Barre syndrome dominated among non-polio AFP (39.3% of cases); more rare were traumatic neuritis (27.9% of cases), transient monoparalysis (12.1%), myelitis (7.6%). Non-polio AFP differed from VAPP by following epidemiological and virological characteristics: predominance of previously repeatedly vaccinated against poliomyelitis; development of paralysis in long-term period after vaccination; isolation of non-polio viruses belonged to three serotypes of Coxsackie B viruses (B1, B4, B6) and six serotypes of Echo viruses (6, 7, 11, 14, 24, 25) in 8.1% of cases; absence of typical for polio residual paralyses in patients who excreted vaccine polioviruses.

[Characterization of poliovirus vaccine strains isolated in the country with high level of immunization coverage]. / Kharakteristika vaktsinnykh shtammov poliovirusa, vydelennykh v strane s vysokim urovnem okhvata immunizatsiei.

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.

[Characterization of the immune status of patients with vaccine-associated poliomyelitis]. / Kharakteristika immunnogo statusa bol'nykh s vaktsinoassotsiirovannym poliomielitom.

Specific humoral immunity, total immune status and typing of HLA antigens, class 1, in loci A and B were studied in children with vaccine-associated paralytic poliomyelitis (VAPP). The immune status investigation revealed that changes in the content of serum immunoglobulins were most frequent. Out of 8 examined children, 5 children had IgA deficiency and 1 child had total variable immunodeficiency. In one case disturbances in cell-mediated immunity prevailed. Tissue typing revealed the presence of HLA A2 and B44 in 5 out of 6 examined children, which considerably exceeded their average occurrence among the Belorussian population. In spite of frequent detection of immunological disturbances in VAPP patients, out of 38 serologically examined children 36 (95%) were found to have virus-neutralizing serum antibodies to poliovirus, which was indicative of the capacity of their immune system for response to the administration of vaccine virus. To minimize the risk of VAPP in children and to achieve the goal of poliomyelitis eradication the combined immunization scheme consisting of 1-3 vaccinations with inactivated poliovaccine with subsequent administration of oral vaccine prepared from attenuated Sabin viruses is regarded as most promising.

[The immunological efficacy of the combined vaccine Trimovax intended for the prevention of measles, mumps and rubella]. / Immunologicheskaia éffektivnost' assotsiirovannoi vaktsiny Trimovaks, prednaznachennoi dlia profilaktiki kori, parotita i krasnukhi.

In 1996 the immunization of children against measles, mumps and rubella with combined vaccine Trimovax ("Pasteur Mérieux Connaught", France) was carried out in the Republic of Belarus. The reactogenicity of the vaccine was studied in 372 children. To evaluate immunological effectiveness, the sera of 324 children were used. Postvaccinal reactions of different intensity were registered in 5.6% of the children; of these, 1.3% exhibited severe reactions. Among the vaccinees, protective titers of antibodies to measles were found in 97.6% to mumps, in 93.8% and to rubella, in 96.0% of the children. Antibodies to all three components of the vaccine were present mainly in high and moderate titers. The results thus obtained indicate that, Trimovax was well tolerated and proved to be immunologically active.