Impact of the rotavirus vaccine on the incidence of diarrhea in children: A study on temporal tendency

In Brazil, a country with very heterogeneous social segments, child mortality rates are still associated with the occurrence of severe diarrhea, particularly in children under two years old. One of the etiological agents involved in such condition is the rotavirus. As from March 2006, the National Immunization Program has included this vaccine in the vaccination calendar for children under two years old to be applied in two doses: at 2 and 4 months of age. This study aimed at analyzing the temporal tendency of acute cases of diarrhea attended to by the Emergency Pediatrics Service of the Botucatu School of Medicine University Hospital, São Paulo State University at Botucatu, from 2003 to 2007. The frequencies of diarrhea over such period were calculated according to age range and gender, and the most frequent symptoms were analyzed. Modeling of this phenomenon was performed by using generalized additive models whose response and predictor variables were, respectively, the frequency of diarrhea and time. For the response variable, it was supposed that such counts followed a Poisson distribution in time. The comparison between the models was carried out through the Poisson regression models for each period. The seasonal pattern observed prior to vaccination disappeared after the commencement of the campaign. These data suggest a change in the patterns of occurrence of diarrhea in children under two years old after the intervention of the vaccine, thus calling attention to its effectiveness as a Public Health measure, and specifically in this case, for diarrhea control in childhood.