Within each pair of twins, Dose 1 and Dose 2 of HRV vaccine/placebo was administered on the same day. In view of providing find protocol benefit to the infants receiving placebo during the course of the study, an additional dose of HRV vaccine was administered to all infants (aged < 6 months) at 7-weeks after the second vaccine/placebo dose in an open-labeled manner. All infants received three doses of combined diphtheria, tetanus, acellular pertussis, hepatitis B, inactivated poliovirus and Haemophilus influenzae

vaccine (DTPa-HBV-IPV-Hib [Infanrix hexa™, GSK Biologicals]). Infants were not allowed to take part in the study if they had received any investigational drug or vaccine 30 days preceding the first study vaccine/placebo dose or had a history of allergic disease likely to be exacerbated by the vaccine or had a history of chronic gastrointestinal diseases. They were also excluded if they were immunosuppressed or had an acute disease at the time of study enrolment. Hypersensitivity

to the vaccine/placebo and intussusception were adverse events that established absolute contraindication to further administration of vaccine/placebo doses. This study was conducted between January 2007 and February 2008, following Good Clinical Practice and the Declaration of Helsinki; the protocol and related documents were reviewed and approved by the ethics committee of the study centers. Parents or guardians of the participating twins provided consent for study participation by signing second the informed consent form. Rotarix™ (HRV) vaccine contained at least 106.0 median cell culture infectious dose of the selleck chemicals vaccine strain per vaccine dose (1 ml). The placebo had the same constituents as the active vaccine but without the vaccine virus and was identical in appearance to the vaccine. The lyophilized vaccine and placebo were reconstituted with the supplied liquid calcium carbonate buffer before oral administration [10]. Presence of the vaccine strain in the placebo group for any of the stool samples collected at pre-determined time points

was considered a positive transmission case. To evaluate rotavirus antigen shedding (ELISA, Dr. Ward’s Lab, USA), stool samples were collected by the parents/guardians in each pair of twins (HRV vaccine/placebo) at pre-determined time points—before the administration of the first and second HRV vaccine/placebo dose (or on the day of vaccination), three times a week (every two days) up to six weeks after each dose of HRV vaccine/placebo and at the post-vaccination blood sampling time point (7 weeks post-Dose 2). To ensure proper stool sample collection, surveillance was performed by a social worker at the time of stool sample collection. The study staff stuck appropriate labels on the stool collection containers to avoid mix-up of samples by the parents/guardians.