Background: RIX4414(Rotarix, a trademark of GlaxoSmithKline), an oral live attenuated human rotavirus (RV) vaccine has previously been shown to be highly effective against RV gastroenteritis(GE). The efficacy evaluation of RIX4414 administered concomitantly with routine EPI vaccinations including Oral Polio Vaccine(OPV) to healthy infants in a phase III, double-blind, randomized, placebo-controlled and multi-center study (444563/024/NCT00139347) conducted in six countries in Latin-America is presented.Methods: Healthy infants aged 6-12 weeks were enrolled to receive two doses of RIX4414(N = 4376) or placebo(N = 2192) according to a 0,1–2 month schedule, administered concomitantly with Dose 1 and Dose 2 of routine pediatric vaccines including OPV, given respecting the national immunisation guidelines.Vaccine efficacy(VE) was calculated from two weeks post-Dose2 until one year of age. Severe GE was defined as an episode of diarrhea requiring hospitalization and/or re-hydration therapy in a medical facility. Diarrhoeal samples were analyzed for RV by ELISA and typed by RT-PCR based method. Safety data were collected throughout the study. Results: During the efficacy follow-up period (mean duration of 7.4 months) RIX4414 has offered 81.6% (95%CI:54.4;93.5) protection against severe RVGE and 88.3% (95%CI:64.0;97.1) against hospitalization due to RVGE. For severe RVGE, VE against wild-type G1 was 100% (95%CI:<0;100) and 80.6% (95%CI:51.4;93.2) against pooled non-G1 RV types (G2,G9). No clinically meaningful difference between RIX4414 group and the placebo group for serious adverse events were reported. Conclusion: Two doses of RIX4414(Rotarix™)offer high protection against severe RVGE and related hospitalizations when co-administered with specific childhood vaccines including OPV. These results show that co-administration with OPV does not impact the efficacy of Rotarix™ and are in line with the high efficacy against severe RVGE of 85% demonstrated in a large Phase III Latin America study with staggered co-administration of OPV. This finding is of significance for the implementation of RV vaccination programmes in many countries where OPV is still routinely administered.