Rotavirus is an important cause of childhood diarrhoea. A monovalent rotavirus vaccine (Rotarix ® ) was introduced into the Immunization Program of Brazil in 2006. In this study, we describe the incidence and burden of disease of rotavirus diarrhoea in two cohorts of children (vaccinated and unvaccinated). We followed two groups of 250 children under one year old, who were enrolled in December 2006 from a low-income residential area inNortheast Brazil. The children were monitored every two weeks for two years. Stool samples from children with diarrhoea were examined for the presence of rotavirus. Rotaviruses were genotyped using real time-polymerase chain reaction. The mean numbers of all-cause diarrhoea episodes/child (adjusted for age) in the first year were 0. 87 and 0.84, in vaccinated and unvaccinated children, respectively. During the second year, the number of episodes/ child decreased to 0.52 and 0.42. Only 16 (4.9%) of 330 stool samples were rotavirus-positive (10 vaccinated and 6 unvaccinated children) and only P[4]G2 rotaviruses were identified. All-cause diarrhoea episodes were more severe in unvaccinated children in the first year of age (p < 0.05), while vaccinated children had more severe episodes 18 months after vaccination. Rotavirus diarrhoea incidence was very low in both groups.
Key words: diarrhoea -rotavirus -vaccine -cohort -children -BrazilRotavirus diarrhoea in vaccinated children • Sarah Cristina Fontes Vieira et al.
331ties were visited at home in 2006 and their parents were invited to enrol their children in the study, independent of their vaccination status. The parents of the first 250 children who had received two oral doses of the Rotarix ® vaccine (GlaxoSmithKline Biologicals, Rixensart, Belgium) at two and four months of age (vaccinated cohort) were invited to participate and a further 250 children who had not received the vaccine comprised the unvaccinated cohort. Vaccination status was verified using the child's vaccination card and the Health Centre's databases. The youngest unvaccinated children registered were selected, despite the fact that the two groups could not be matched by age, as unvaccinated children had to be ineligible for vaccination at the time of enrolment, and therefore at least four months of age. Unvaccinated children serving as the control group were not offered the vaccine due to EPI guidelines that exclude children greater than or e�ual to four months of age to avoid the risk of intussusception among older infants (WHO 2007).After obtaining informed parental consent, all children were visited at home for the following two years, independently of their age at the time of enrolment. Visits were conducted every two weeks by three trained interviewers who in�uired as to whether or not the child had experienced diarrhoea episodes during the previous twoweek period. If the parent indicated that the child had diarrhoea, the interviewer collected information regarding the date of the episode and clinical presentation. The severity of the diarrhoea episodes wa...