This might be explained by the observation that high titers of the remaining transplacental antibody against Modulators rotavirus can inhibit the immune response to the 2nd dose of vaccine in the 8-12-16-week schedule. Steele found that 2 doses of Rotarix™ given GSK J4 chemical structure at 10 and 14 weeks performed as well as 3 doses given

at 6, 10, and 14 weeks but better than 2 doses given at 6 and 10 weeks [15]. In other words, the older the infant was when he received the vaccine, the lower was the initial titer of transplacental antibody and the better the immune response to the vaccine [16]. In both the 2 and the 3 dose schedules in our study, last dose was administered when the infant was the same age, i.e. 18 weeks (95%CI (16.6–19.2)), unlike studies with the Rotarix™ vaccine where a third dose was added to the schedule at 14 weeks. Therefore, the immune response to 2 doses of the high titer Rotavin-M1 vaccine at 2-month interval yielded the most robust immune response. Of the same notes, an interval of 2 months between doses was more efficient in inducing immune response compared to a 1-month LY2157299 price interval in

both low and higher titer formulation. Similar observations were documented when the liquid form Rotarix™ was tested in Vietnamese children [7]. In that study, 2 doses of Rotarix™, delivered 1 month apart gave a seroconversion rate of 63.3% at 1 month after the 2nd vaccine dose. The same 2 dose vaccine however, when delivered 2 months apart gave a seroconversion rate of 81.5%.

Application of this 2-month interval between 2 doses of Rotarix™ in European countries such as Spain, Italy and Finland led to high seroconversion rates of 92.3–94.6% [17]. Thus again, the higher immune response with this 2-month schedule might be associated with the slightly older children who are immunologically more mature compared to those with the 1-month Levetiracetam schedule [7]. The immune responses induced by Rotavin-M1 are comparable to those seen in the Rotarix™ group in this study and in a previous study that employed the liquid form of the vaccine with a similar schedule (58–63.3%) [7]. It is noted that the pattern of IgA response to rotavirus vaccine in Vietnam seems to follow the trend of developing countries. In particular, the IgA responses to Rotarix™ in Brazil, Mexico, Venezuela and Vietnam were reported at 61–65%, which are lower than those in USA, Canada, Europe and Singapore (78.2–88.3%) [18], [19], [20] and [21] and higher than those in Malawi and South Africa [22]. In particular, when Rotarix™ is introduced in the expanded immunization program of European countries such as France, Germany, Spain and Czech republic, the IgA response rates were very high, 82–94.6% [17]. In Singapore the response was 76–91% depending on the vaccine titers [23] and [24].