RESEARCH ARTICLE The effect of introduction of routine immunization for rotavirus vaccine on paediatric admissions with diarrhoea and dehydration to Kenyan Hospitals: an interrupted time series study [version 1; peer review: 2 approved with reservations] Daisy Chelangat 1,2 , Lucas Malla 3 , Reuben C. Langat 2 , Samuel Akech 1 , Clinical Information Network Author Group 1 Health Services Unit, KEMRI-Centre of Geographic Medicine Research-Coast/ KEMRI-Wellcome Trust Research Programe, Nairobi, Kenya 2 Department of Mathematics and Computer Science, University of Kabianga, Kericho, Kenya 3 Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, London, London, WC1E7HT, UK First published: 04 Jan 2022, 7:2 https://doi.org/10.12688/wellcomeopenres.17420.1 Latest published: 04 Jan 2022, 7:2 https://doi.org/10.12688/wellcomeopenres.17420.1 v1 Abstract Background: Dehydration secondary to diarrhoea is a major cause of hospitalization and mortality in children aged less than five years. Most diarrhoea cases in childhood are caused by rotavirus, and routine introduction of rotavirus vaccine is expected to reduce the incidence and severity of dehydration secondary to diarrhoea in vaccinated infants. Previously, studies have examined changes in admissions with stools positive for rotavirus but this study reports on all admissions with dehydration secondary to diarrhoea regardless of stool rotavirus results. We aimed to assess the changes in all-cause severe diarrhoea and dehydration (DAD) admissions following the vaccine’s introduction. Methods: We examined changes in admissions of all clinical cases of DAD before and after introduction of routine vaccination with rotavirus vaccine in July 2014 in Kenya. We use data from 13 public hospitals currently involved in a clinical network, the Clinical Information Network (CIN). Routinely collected data for children aged 2-36 months were examined. We used a segmented mixed effects model to assess changes in the burden of diarrhoea and dehydration after introduction of rotavirus vaccine. For sensitivity analysis, we examined trends for non-febrile admissions (surgical or burns). Results: There were 17,708 patients classified as having both diarrhoea and dehydration. Average monthly admissions due to DAD for each hospital before vaccine introduction (July 2014) was 35 Open Peer Review Approval Status 1 2 version 1 04 Jan 2022 view view Mavuto Mukaka, Mahidol University, Bangkok, Thailand 1. Daniel Hungerford , University of Liverpool, Liverpool, UK 2. Any reports and responses or comments on the article can be found at the end of the article. Page 1 of 14 Wellcome Open Research 2022, 7:2 Last updated: 09 FEB 2023