Characteristics of intussusception among children in Hokkaido, Japan, during the pre- and post-rotavirus vaccine eras (2007-2016)

Aim: To analyse the epidemiology of intussusception in Hokkaido Prefecture, Japan during a 10 -year period spanning the introduction of the rotavirus (RV) vaccine (2007- 2016). Methods: Using a standard questionnaire, a retrospective surveillance was conducted across 17 hospitals with paediatric beds in Hokkaido Prefecture. We compared the data between the pre-vaccine era (2007- 2011) and post-vaccine era (2012- 2016). Results: In total, 208 and 110 intussusception cases were in the pre-and post-vaccine eras, respectively. A significant reduction of the intussusception incidence in children aged < 1 year was observed from the pre-to the post-vaccine era (102.4- 56.5 per 100 000 infants; incidence rate ratio, 0.55; p = 0.004). There was a relatively high -positive RV antigen detection rate (29.4%, 5/17) during the RV epidemic period in Japan (March- May) in the pre-vaccine era. None of the intussusception cases in the 31 patients with a history of RV vaccination occurred within 1 month after the admin-istration of an RV vaccine dose. Conclusions: The incidence of intussusception in children aged < 1 year decreased sig-nificantly after RV vaccine introduction in Japan. Another survey is needed to deter-mine how the incidence of intussusception has changed further since the introduction of routine RV vaccination in 2020.