Background: In 2012, Fiji became the first independent Pacific island country to introduce rotavirus vaccine. We describe the impact of rotavirus vaccine on all-cause diarrhoea admissions in all ages, and rotavirus diarrhoea in children < 5 years of age. Methods: An observational study was conducted retrospectively on all admissions to the public tertiary hospitals in Fiji (2007-2018) and prospectively on all rotavirus-positive diarrhoea admissions in children < 5 years at two hospital sites (2006-2018, and 2010-2015), along with rotavirus diarrhoea outpatient presentations at one secondary public hospital (2010-2015). The impact of rotavirus vaccine was determined using incidence rate ratios (IRR) of all-cause diarrhoea admissions and rotavirus diarrhoea, comparing the pre-vaccine and post-vaccine periods. All-cause admissions were used as a control. Multiple imputation was used to impute missing stool samples. Findings: All-cause diarrhoea admissions declined among all age groups except among infants ≤2 months old and adults ≥55 years. For children < 5 years, all-cause diarrhoea admissions declined by 39% (IRR) = 0 • 61, 95%CI; 0 • 57-0 • 65, p-value < 0 • 001). There was an 81% (95%CI; 51-94%) reduction in mortality among all-cause diarrhoea admissions in children under < 5 years. Rotavirus diarrhoea admissions at the largest hospital among children < 5 years declined by 87% (IRR = 0 • 13, 95%CI; 0 • 10-0 • 17, p-value < 0 • 001). Among rotavirus diarrhoea outpatient presentations, the IRR was 0 • 39 (95%CI; 0 • 11, 1.21, p-value = 0.077). Interpretations: Morbidity and mortality due to rotavirus and all-cause diarrhoea in Fiji has declined in people aged 2 months to 54 years after the introduction of the RV vaccine.

The introduction of the rotavirus vaccine, Rotarix, into the Fiji National Immunisation Program in 2012 has reduced the burden of rotavirus disease and hospitalisations in children less than 5 years of age. The aim of this study was to describe the pattern of rotavirus genotype diversity from 2005 to 2018; to investigate changes following the introduction of the rotavirus vaccine in Fiji. Faecal samples from children less than 5 years with acute diarrhoea between 2005 to 2018 were analysed at the WHO Rotavirus Regional Reference Laboratory at the Murdoch Children’s Research Institute, Melbourne, Australia, and positive samples were serotyped by EIA (2005–2006) or genotyped by heminested RT-PCR (2007 onwards). We observed a transient increase in the zoonotic strain equine-like G3P[8] in the initial period following vaccine introduction. G1P[8] and G2P[4], dominant genotypes prior to vaccine introduction, have not been detected since 2015 and 2014, respectively. A decrease in rotavirus genotypes G2P[8], G3P[6], G8P[8] and G9P[8] was also observed following vaccine introduction. Monitoring the rotavirus genotypes that cause diarrhoeal disease in children in Fiji is important to ensure that the rotavirus vaccine will continue to be protective and to enable early detection of new vaccine escape strains if this occurs.

The surveillance of enteric pathogens is critical in assessing the burden of diarrhoeal disease and informing vaccine programs. Surveillance supported by the World Health Organization in Fiji, Vietnam, the Lao People’s Democratic Republic, and the Philippines previously focussed on rotavirus. There is potential to expand surveillance to encompass a variety of enteric pathogens to inform vaccine development for norovirus, enterotoxigenic Escherichia coli and Shigella.