Josephine van Dongen

Chapter 4 98 vaccination status. Data analysis were performed using the statistical software of RStudio version 3.6.1. Packages; survminer, survival, lme4, rstanarm, timeseries . Ethical approval The medical ethic board of the University Medical Center Utrecht declared that the RIVAR study was not covered by the Medical Research Involving Human Subjects Act. Rotavirus vaccine was implemented into routine care and study procedures were non-invasive. Results Between November 2014 and April 2016, a total of 13 hospitals with 15 locations star ted in the pre-implementation period of the RIVAR project and subsequently implemented rotavirus vaccination between May 2016 and November 2017.Throughout the project a total of 2,484 medical risk infants in the pre-implementation and 2,878 in the post-implementation period met the eligibility criteria ( figure 2 ). Between November 2014 and April 2016, 631 of these high-risk infants were recruited in the ‘before’ cohor t and contributed to 9,125 person-months of observation. An additional 851 high-risk infants were enrolled in the ‘after’ cohor t, between May 2016 and July 2018, and contributed to 12,302 person-months. Follow-up of the last cohor t participant was completed in December 2019. Among 1,482 cohor t par ticipants 1,302 infants were born premature, 447 were small for gestational age and 251 had one or more congenital disorders.The median length of postnatal hospital stay was 28 days (interquar tile range [IQR], 38 days) and total median number of hospitalization days (including initial admission) during follow-up was 34 (IQR 44 days). The characteristics of par ticipants in the before and after cohor t were comparable ( table 1 ). There was a small difference in the par ticipation rate in the national immunization program (seven percent less par ticipation in the HRV vaccinated group) and in completeness of follow- up (number of par ticipants with complete follow-up is 14% lower in HRV vaccinated group). 719 infants in the after cohor t were HRV immunized, for 599 infants information on receiving the second dose administration was available (83.3%). A total of 1,223 AGE episodes were identified during follow-up, table 2. A fecal sample was collected from 564 (46.1%) episodes. Rotavirus was detected in 117 AGE samples (20.7%). Severe ( ≥ 11 Vesikari score) rotavirus positive AGE occurred in 18 infants in the before cohor t and 20 infants in the after cohor t. Hospitalization due to rotavirus AGE was repor ted in two versus two infants.