intussusception was determined to in fact be ileoileal with a Meckel's diverticulum acting as a lead point which was resected; ileocolic intussusception with a 1.1 cm echogenic mass lesion; vomiting/episode of non bilious emesis; lethargy; refused baby food; less interactive; sleeping more; small bowel movement and decreased wet diapers; non bilious projectile vomiting; dehydration concerns; dilated loops of bowel; dilated loops of bowel suggestive of obstruction; bowel sounds were present; This serious case was reported in a literature article and described the occurrence of ileocolic intussusception in a 5-month-old male patient who received Rotavirus vaccine for prophylaxis.    On an unknown date, the patient received Rotavirus vaccine. On an unknown date, an unknown time after receiving Rotavirus vaccine, the patient experienced ileocolic intussusception (Verbatim: ileocolic intussusception with a 1.1 cm echogenic mass lesion) (serious criteria hospitalization, GSK medically significant and clinically significant/intervention required), meckel's diverticulum (Verbatim: intussusception was determined to in fact be ileoileal with a Meckel's diverticulum acting as a lead point which was resected) (serious criteria hospitalization and clinically significant/intervention required), vomiting (Verbatim: vomiting/episode of non bilious emesis) (serious criteria hospitalization), lethargy (Verbatim: lethargy) (serious criteria hospitalization), appetite absent (Verbatim: refused baby food) (serious criteria hospitalization), decreased activity (Verbatim: less interactive) (serious criteria hospitalization), hypersomnia (Verbatim: sleeping more) (serious criteria hospitalization), bowel movement irregularity (Verbatim: small bowel movement and decreased wet diapers) (serious criteria hospitalization), vomiting projectile (Verbatim: non bilious projectile vomiting) (serious criteria hospitalization), dehydration (Verbatim: dehydration concerns) (serious criteria hospitalization), intestinal dilatation (Verbatim: dilated loops of bowel) (serious criteria hospitalization), intestinal obstruction (Verbatim: dilated loops of bowel suggestive of obstruction) (serious criteria hospitalization and GSK medically significant) and abnormal bowel sounds (Verbatim: bowel sounds were present) (serious criteria hospitalization). The outcome of the ileocolic intussusception, meckel's diverticulum, vomiting, lethargy, appetite absent, decreased activity, hypersomnia, bowel movement irregularity, vomiting projectile, dehydration, intestinal dilatation, intestinal obstruction and abnormal bowel sounds were not reported.   The reporter considered the ileocolic intussusception, meckel's diverticulum, vomiting, lethargy, appetite absent, decreased activity, hypersomnia, bowel movement irregularity, vomiting projectile, dehydration, intestinal dilatation, intestinal obstruction and abnormal bowel sounds to be unlikely related to Rotavirus vaccine.   The company considered the ileocolic intussusception, meckel's diverticulum, vomiting, lethargy, appetite absent, decreased activity, hypersomnia, bowel movement irregularity, vomiting projectile, dehydration, intestinal dilatation, intestinal obstruction and abnormal bowel sounds to be unlikely related to Rotavirus vaccine.   Additional Information: GSK Receipt Date: 16-Jun-2023 The patient was born at 39 weeks presented with vomiting and lethargy. On the day of presentation, the patient took the morning bottle but refused baby food, then had an episode of non-bilious emesis. Over the course of the day the patient was less interactive and sleeping more. The last bottle was taken at noon. There was one small bowel movement and decreased wet diapers. At 7:30 PM the patient had an episode of non-bilious projectile vomiting. Due to new projectile vomiting, lethargy, and dehydration concerns, parents brought the child to a local emergency department (ED) for evaluation. In the ED, there was another episode of projectile vomiting. Additional history included a pediatrician visit five days prior to admission where the patient received vaccinations including for rotavirus. An x-ray of the abdomen showed dilated loops of bowel suggestive of obstruction, therefore the patient was transferred to the hospital for further management. On admission, the patient was non-toxic appearing with a soft abdomen that did not appear distended and bowel sounds were present. An ultrasound was obtained which showed ileocolic intussusception with a 1.1 cm echogenic mass lesion acting as a lead point. Surgery was consulted, and operative management was recommended. Intraoperatively the intussusception was determined to in fact be ileoileal with a Meckel's diverticulum acting as a lead point, which was resected. The proximal small bowel was dilated and when the diverticulum was opened the small bowel contents were noted to be fecalized and malodorous, but all bowel was viable. The patient was separately noted to have malrotation, and a Ladd's procedure was performed. Post-operatively the patient did well. The patient was initially managed with total parenteral nutrition (TPN) awaiting return of bowel function but was tolerating full feeds and ready for discharge on post-operative day 8.  Although historically the rotavirus vaccine had been associated with an increased incidence of intussusception, the risk was very low with current formulations. The presence of a Meckel's diverticulum, the most common lead point, makes it unlikely that the vaccine contributed to this patient's presentation. Finally, this patient was found to have both a Meckel diverticulum and intestinal malrotation. Clinicians must maintain a high index of suspicion for abdominal emergencies such as intussusception in younger infants whose signs and symptoms may be more subtle. This case highlights a previously described but uncommon association between intestinal malrotation and Meckel diverticulum.