Clinical Severity of Gastroenteritis in Children Hospitalized With Rotavirus Infection Before and Post Introduction of a National Rotavirus Vaccination Program in Australia.

Abstract

There have been dramatic reductions in emergency department visits and hospital admissions for gastroenteritis in young children following the introduction of rotavirus vaccination, into the National Immunisation (NIP) program in Australia since May 1, 2007.1,2 However, the diversity of rotavirus strains causing disease in Australia has increased following introduction of the rotavirus vaccine program, with postvaccination era predominant strains varying between states implementing RV1 (Rotarix; GlaxoSmithKline Biologicals, Belgium) versus RV5 (RotaTeq; Merck & Co. Inc., Whitehouse Station, New Jersey 08889, USA) vaccine, illustrating the need for continued surveillance and monitoring of rotavirus disease and severity.3 To explore the impact of vaccination on clinical severity of rotavirus disease, we reviewed all laboratory confirmed rotavirus admissions to the Women’s and Children’s Hospital, a tertiary pediatrics hospital in South Australia, for children under 5 years of age during 2 time periods (prevaccine introduction: May 1, 2005–April 3, 2007 and postvaccine introduction May 1, 2009–April 30, 2013). Medical records were reviewed to determine the severity of rotavirus infections assessed using the Vesikari Clinical Severity Scale, VCSS4 and vaccination history was ascertained from the Australian Immunisation Register (AIR). Nosocomial infections were excluded, and readmissions to hospital within 72 hours were considered 1 event. Research ethics approval was obtained from the Women’s and Children’s Health Network Human Research Ethics Committee (REC322A). A total of 233 pre- and 79 postvaccination period rotavirus admissions were identified and assessed. The proportion of children 6 months to 2 years of age requiring hospitalization reduced significantly in the postvaccination period compared with the prevaccination period [pre: 136/233 (58.4%) vs. post: 15/79 (19.0%), P < 0.001]. The median age at admission increased from 18 months [interquartile range (IQR) 12–27 months] in the prevaccination period to 29 months (IQR 14–44 months) in the postvaccination period. Vaccination status was confirmed for 75/79 of the postvaccine period cases. Of these, 36/75 (48.0%) were ineligible for rotavirus vaccination due to either being too young (n = 7) or being born before introduction of the funded vaccine schedule in Australia (n = 29). However, 16/75 (21%) children, with ages ranging from 14 to 55 months, had received all 3 doses of the rotavirus vaccine before hospitalization. The average duration of hospital stay was 24 hours for both review periods. The majority of rotavirus admissions were classified as severe (VCSS ≥ 11) in both the pre- and postvaccination periods (88.4% vs. 83.8%, P = 0.34); however, the mean VCSS was significantly lower for vaccinated versus unvaccinated children [VCSS: 12.3 (95% CI 10.8–13.7) vs. 14.0 (95% CI 13.2–14.9) respectively, P = 0.03]. The proportion scoring severe in the postvaccination period was also reduced for those who had received at least 1 dose of rotavirus vaccine [20/27 (74%) vs. 40/44 (91%), P = 0.06]. Despite continuing rotavirus hospitalizations following implementation of the national rotavirus vaccination program, there was a clear reduction of cases in the 6-month to 2-year-age group and an increase in the median age at admission. The majority of children hospitalized for rotavirus in the postvaccination period were unvaccinated, and for those vaccinated, there was evidence of reduced clinical severity. ACKNOWLEDGMENTS All authors acknowledge that the paper has not been submitted for consideration elsewhere, that its publication is approved by all authors. Michelle Clarke, BAppSc(MedLab), GDSTC, MPPH,*†‡Ying Ying Liew, MBBS, FRACGP, DCH,§Suja Mary Mathew, MBBS, MD, FRACP,*Helen Siobhan Marshall, MBBS, DCH, MPH, MD*†‡From the *Vaccinology and Immunology Research Trials Unit, Women’s and Children’s Health Network, North Adelaide, South Australia 5006, Australia;†Adelaide Medical School, The University of Adelaide, South Australia 5006, Australia;‡Robinson Research Institute, The University of Adelaide, South Australia, 5006, Australia;§Previously employed at Vaccinology and Immunology Research Trials Unit, Women’s and Children’s Hospital, North Adelaide, South Australia 5006, Australia.