Epidemiological Shifts in Severe Acute Gastroenteritis in US Children: Will Rotavirus Vaccination Change the Picture?
Article Outline
Abbreviations: AGE, Acute gastroenteritis, ED, Emergency Department
Diarrhea remains a leading cause of morbidity among US children, accounting for approximately 10% of all inpatient admissions in US children younger than 5 years of age.1, 2 However, the epidemiology of severe diarrhea in US children, especially the large fraction of disease attributable to viral agents, is changing. New vaccines targeting rotavirus gastroenteritis—the principal cause of severe diarrhea in US children and a major cause of death among children younger than 5 years of age around the globe3—are now licensed and widely used in the United States. Our understanding of the etiologic role of noroviruses in childhood diarrhea and their antigenic drift, similar to that of influenza viruses, is improving due to advances in and the wider availability of diagnostic assays for these agents.4 Finally, recent advances in the field of viral pathogen discovery have led to intriguing questions about the role of novel and emerging pathogens, such as human bocaviruses, in childhood diarrhea.5 Although some explanations for changes in the epidemiology of diarrheal disease are more evident than others, these recent occurrences may alter how we research, detect, remediate and understand severe childhood diarrhea among US children in the near future.
See related article, p 777
In this issue of The Journal,6 Pont et al have analyzed a 10-year retrospective cohort of children ages 0 to 18 years enrolled in the Tennessee expanded Medicaid program, TennCare, to determine diarrhea-associated health care usage patterns. Administrative data recording diarrhea-associated visits from 1995 to 2004 were studied to calculate annual rates of diarrheal healthcare encounters in hospital, emergency department (ED), and outpatient settings. The contribution of rotavirus gastroenteritis to these rates was estimated using the “winter residual method,” a previously used approach in which excess events during the winter months relative to a summer baseline are attributed to rotavirus.7 This study fills a gap in understanding the burden of diarrhea among children enrolled in an expanded Medicaid program, representing an understudied and sizable socioeconomic stratum of children from low income and working poor families (39% of Tennesseean children were enrolled in TennCare in 2000, according to this paper). The analysis also demonstrates the considerable health burden of diarrhea on pediatric EDs and outpatient clinics, in addition to the well documented burden of inpatient admissions that have been the focus of previous evaluations.
The rates of diarrhea-associated outpatient visits and inpatient admissions reported in this study are comparable to those in earlier evaluations. However, the ED rates for diarrheal illnesses among TennCare children nearly doubled from 1995 to 2004, and these rates appeared to be 5-fold greater than those reported in a population of children enrolled in 4 West Coast managed-care organizations during 1992 to 1994.8 Despite this elevation in TennCare ED rates, hospitalization and outpatient visit rates for diarrheal illnesses remained constant over time, suggesting that EDs were not simply absorbing cases from hospitals or clinics due to payer-pressures or improved clinical treatment regimens.
Pont et al speculate that the elevation in ED rates for diarrhea may be partially explained by an increased disease burden over time due to pathogens such as norovirus or changes in medical care usage patterns. The authors acknowledge that more study is needed to address this issue, and future evaluations should also assess possible changes in medical coding patterns (ie, primary versus associated diagnostic codes) and billing practices (eg, admissions billed as short stay events that may be included in ED data). In addition, data from other state and national administrative databases could be evaluated to confirm the trends observed in this study.
Importantly, the study by Pont et al encompasses an interval of time preceding the licensure of both the pentavalent human-bovine reassortant rotavirus vaccine, RotaTeq (Merck and Company; Whitehouse Station, New Jersey), and Rotarix (GlaxoSmithKline Biologicals; Rixensart, Belgium), a monovalent live attenuated human rotavirus vaccine. Therefore, the data could provide a baseline for understanding possible epidemiological and healthcare utilization changes due to rotavirus vaccination among a lower socioeconomic childhood population.
Although Pont et al's 10-year trendline terminates in 2004, a recent report9 compares postlicensure childhood acute gastroenteritis (AGE) surveillance data for 2008 with previous years of AGE surveillance with noteworthy implications. From January through April 2008, a period of time approximately 2 years after US licensure of RotaTeq, an astonishing 79% decline in rotavirus detection was reported from sentinel laboratories participating in the US National Respiratory and Enteric Virus Surveillance System compared with 15 years of previous data. Additionally, a population-based surveillance network, the New Vaccine Surveillance Network (which incidentally includes Davidson County, Tennessee), detected an approximate 90% decline in severe rotavirus gastroenteritis visits to the hospital, ED, and outpatient providers during these months in 2008 compared with the previous two years. Both of these surveillance systems have registered nearly 40% reductions in all-cause AGE between January and May 2008 compared with previous years of systematically collected data. Similar levels of decline for all-cause AGE were observed in the large clinical trials of both of these vaccines as well.10, 11 Thus, future healthcare utilization trends for AGE illnesses in US children could well be substantially impacted by the rotavirus vaccination program and administrative databases such as the TennCare database should allow us to document this impact.
Understanding the impact of AGE disease trends will require continued surveillance and epidemiological research. Ecologic trends using large administrative databases will be valuable in documenting the potential influence of the US rotavirus vaccination program and establishing hypotheses for further study. Reduction in AGE outcomes may be seen primarily in infants younger than 1 year in the first year of vaccine introduction, in those younger than 2 years in the second year of the rotavirus vaccination program, and in incrementally increasing age groups during successive years. Such trend evaluations should account for some natural year-to-year variation in rotavirus disease burden that is known to occur in the absence of vaccination. The most reliable estimates of rotavirus vaccine effectiveness, however, will be calculated through direct methodologies such as case-control studies and case-cohort studies. Ideally, these vaccine effectiveness evaluations will use laboratory-confirmed rotavirus disease status and medical chart confirmed vaccination status, and will have acceptable epidemiological study power across geographic locations.
We have entered an era in the history of diarrheal illness wherein new tools for the prevention and study of important diarrheal pathogens are available. We must better clarify the roles of known, newly discovered, and recently evolved diarrheal pathogens upon our children's health and health care utilization, and document the impact of new rotavirus vaccines on AGE disease burden.
References
- Hospitalizations associated with rotavirus diarrhea in the United States, 1993 through 1995: surveillance based on the new ICD-9-CM rotavirus-specific diagnostic code. J Infect Dis. 1998;177:13–17
- Hospitalizations associated with rotavirus gastroenteritis in the United States, 1993-2002. Pediatr Infect Dis J. 2006;25:489–493
- . Global illness and deaths caused by rotavirus disease in children. Emerg Infect Dis. 2003;9:565–572
- . Food-Borne Viruses: State of the Art. In: Koopmans MPG, Cliver DO, Bosch A editor. Food-Borne Viruses: Progress and Challenges. Washington, DC: ASM Press; 2008;p. 29–64
- . Human bocavirus: a new viral pathogen. Clin Infect Dis. 2007;44:911–912
- Trends in healthcare usage attributed to diarrhea, 1995-2004. J Pediatr. 2008;153:777–782
- . Trends in hospitalizations for diarrhea in United States children from 1979 through 1992: estimates of the morbidity associated with rotavirus. Pediatr Infect Dis J. 1996;15:397–404
- Epidemiology of diarrheal disease among children enrolled in four West Coast health maintenance organizations: Vaccine Safety Datalink Team. Pediatr Infect Dis J. 1998;17:605–611
- . Delayed onset and diminished magnitude of rotavirus activity: United States, November 2007-May 2008. MMWR. 2008;57:697–700
- Efficacy and safety of an oral live attenuated human rotavirus vaccine against rotavirus gastroenteritis during the first 2 years of life in Latin American infants: a randomized, double-blind, placebo-controlled phase III study. Lancet. 2008;371:1181–1189
- Safety and efficacy of a pentavalent human-bovine (WC3) reassortant rotavirus vaccine. N Engl J Med. 2006;354:23–33
Disclaimer: The findings and conclusions in this report are those of the author and do not necessarily represent the views of the Centers for Disease Control and Prevention.
PII: S0022-3476(08)00686-0
doi:10.1016/j.jpeds.2008.08.012
Published by Elsevier Inc.
Refers to article:
- Trends in Healthcare Usage Attributable to Diarrhea, 1995-2004 , 11 August 2008
