Group A rotavirus genotypes circulating prior to implementation of a National Immunization Program in Estonia.

Group A rotaviruses (RVA) are a major cause of acute gastroenteritis in children ≤ 5 y worldwide which could be prevented with two recently introduced vaccines - monovalent Rotarix (live-attenuated G1P[8] strain) and pentavalent RotaTeq (human-bovine reassortant containing serotypes G1, G2, G3, G4 and P[8]). Prior to implementation of vaccines into national immunization program we aimed to describe RVA genotype distribution in hospitalized children aged < 5 y in Estonia during 2007-2008. A total of 671 children with confirmed RVA gastroenteritis from three major pediatric hospitals were prospectively enrolled. G- and P-genotypes were detected from 124 stool samples by semi-nested reverse transcription-PCR. Severity of disease was assessed using Clark scoring system. The majority of cases (65%) occurred in infants aged 7 to 24 mo and were of moderate severity (mean Clark score 12.1 (SD 3.2)). The prevailing strain was G2P[4] (34.7%), causing significantly more cases than G4P[8] (12.9%), G1P[8] or G9P[8] (both 4.0%), G3P[8] (1.6%). Yearly differences in genotype distribution occurred, as G2P[4] (52.8%) dominated in 2007, but G4P[8] (26.9%) in 2008. One third of strains remained non-typeable. The distribution of RVA genotypes in Estonia differs from that seen in other Central and Eastern European countries, although one should bear in mind the large proportion of P-untypeable strains and natural fluctuations of dominating RVA genotypes. Nevertheless, considering the high genotype-independent efficacy of the vaccines, introduction of national immunization should be considered.

Pertussis outbreak in a basic school in Estonia: description, contributing factors and vaccine effectiveness.

The aim of the current study was to assess the epidemiological situation concerning the emergence of a pertussis outbreak, as well as potential contributing factors and vaccine effectiveness. A retrospective epidemiological description and an analysis of the outbreak among students were performed. The basic school in Adavere had a total of 150 students in 2003. Of these, 54 cases of pertussis, with median age 12 y, all corresponding to clinical case definition, were identified with an attack rate of 36%. Regarding confirmation of the diagnosis, out of all clinical cases, 18 were confirmed by laboratory testing (2 by isolation of B. pertussis and 16 serologically based on single sera) and 36 with epidemiological linkage only. Of all the students with pertussis, 35 (65%) had received 4 doses and 6 (11%) 3 doses of DTwP vaccine; 13 (24%) students had received fewer than 3 doses or were unvaccinated. The contributing factors in generating this outbreak were close epidemiological contacts, late identification of pertussis diagnosis in the primary, secondary and later cases, as well as a too late initiated active surveillance. In this outbreak, low vaccine effectiveness and low vaccination coverage also played an important role.