HCP reported a patient (infant) of his had a "reaction" after 1st dose of ROTATEQ, which was described as "increased frequency of bowel movements" and "streaks of blood and mucus in the stool"; HCP reported a patient (infant) of his had a "reaction" after 1st dose of ROTATEQ, which was described as "increased frequency of bowel movements" and "streaks of blood and mucus in the stool"; HCP reported a patient (infant) of his had a "reaction" after 1st dose of ROTATEQ, which was described as "increased frequency of bowel movements" and "streaks of blood and mucus in the stool"; the mother had called their office reporting that the infant had been "fussy" and was having "frequent bowel movements and blood and mucus in the stool" as had been noted after the 1st dose of ROTATEQ.; the mother had called their office reporting that the infant had been "fussy" and was having "frequent bowel movements and blood and mucus in the stool" as had been noted after the 1st dose of ROTATEQ.; the mother had called their office reporting that the infant had been "fussy" and was having "frequent bowel movements and blood and mucus in the stool" as had been noted after the 1st dose of ROTATEQ.; HCP told the mother to stop ingesting dairy and soy products because these gastrointestinal issues can be seen in infants that are having a "dairy allergy, usually to cow's milk".; the mother had called their office reporting that the infant had been "fussy" and was having "frequent bowel movements and blood and mucus in the stool" as had been noted after the 1st dose of ROTATEQ.; This spontaneous report was received from a physician, referring to an infant male patient. The patient's concomitant medications were not reported.   The physician reported that, at the age of 2-3 weeks the infant experienced gastrointestinal symptoms, that included mucus in stool, at this time, it was confirmed by the reporter that the patient did not receive the vaccine of rotavirus vaccine, live, oral, pentavalent (ROTATEQ), but was diagnosed with milk protein allergy. The patient's mother changed the diet of infant by herself, and the symptoms were resolved.   On an unknown date, the patient was vaccinated with the first dose of rotavirus vaccine, live, oral, pentavalent (ROTATEQ), administered by oral route, as prophylaxis (formulation, strength, lot number and expiration date were not reported).   On approximately 10-SEP-2020 (also reported as "2-3 weeks ago"), the patient experienced a reaction, which was described as "increased frequency of bowel movements" (frequent bowel movements) and "streaks of blood and mucus in the stool" (haematochezia and mucous stools), at this time; the patient was strictly breast fed, as a precaution the physician recommended to the patient's mother stopped the ingest dairy and soy products (food allergy), because these gastrointestinal issues could be saw in infants that were having a dairy allergy usually to cow's milk. The physician reported that, the patient's mother stopped all dairy and soy intake and the infant had improved by his 2 month well visit.   On an unspecified date in 2020, at the age of 2 months, the patient received the second dose of rotavirus vaccine, live, oral, pentavalent (ROTATEQ), administered by oral route, as prophylaxis (formulation, strength, lot number and expiration date were not reported), however; within 24 hours the patient's mother had call to their office reporting that the infant had been "fussy" (irritability), and was having "frequent bowel movements and blood and mucus in the stool" (frequent bowel movements, haematochezia and mucous stools) as had been noted after administered the first dose.   The physician felt that rotavirus vaccine, live, oral, pentavalent (ROTATEQ) may caused gastrointestinal symptoms in babies with milk protein allergy.   The outcome of frequent bowel movements, haematochezia and mucous stools, regarding with the administration of the first dose was recovered; the outcome of food allergy was not provided, the outcome of frequent bowel movements, haematochezia and mucous stools, regarding with the administration of the second dose was not reported. The causal relationship between rotavirus vaccine, live, oral, pentavalent (ROTATEQ) with the events frequent bowel movements, haematochezia and mucous stools was reported as related, and with the event of food allergy and irritability was not provided.   Upon internal review, haematochezia was determined to be medically significant event.