Impact of the introduction of rotavirus vaccine on hospital admissions for diarrhoea among children in Kenya: A controlled interrupted time series analysis

INTRODUCTION: Monovalent rotavirus vaccine, RotarixTM, was introduced in Kenya in July 2014, is recommended to infants as oral doses at ages 6 and 10 weeks. A multi-site study was established in two population based surveillance sites to evaluate vaccine impact on the incidence of rotavirus-associated hospitalisations (RVH). METHODS: Hospital-based surveillance was conducted from January 2010 to June 2017 for acute diarrhoea hospitalisations among children aged <5 years in two health facilities in Kenya. A controlled interrupted time series analysis was undertaken to compare RVH pre and post vaccine introduction using rotavirus negative cases as a control series.  The change in incidence post vaccine introduction was estimated from a negative binomial model that adjusted for secular trend, seasonality and multiple health worker industrial actions (strikes). RESULTS: Between January 2010 and June 2017 there were 1513 and 1652 diarrhoea hospitalisations in Kilifi and Siaya; among those tested for rotavirus, 28% (315/1142) and 23% (197/877) were positive, respectively.  There was a 57% (95% CI: 8 to 80) reduction in RVH observed in the first year post vaccine introduction in Kilifi and a 59% (95% CI: 20 to 79) reduction in Siaya. In the second year, RVH decreased further at both sites, 80% (95% CI: 46 to 93) reduction in Kilifi and 82% reduction in Siaya (95% CI: 61 to 92), and this reduction was sustained at both sites into the third year. CONCLUSIONS: A substantial reduction of RVH and all-cause diarrhoea has been observed in two demographic surveillance sites in Kenya within 3 years of vaccine introduction.