Shaded areas highlight the months with the highest number of rotavirus hospitalizations prevaccine. Error bars indicate the 95% confidence intervals.
Gastañaduy PA, Curns AT, Parashar UD, Lopman BA. Gastroenteritis Hospitalizations in Older Children and Adults in the United States Before and After Implementation of Infant Rotavirus Vaccination. JAMA. 2013;310(8):851-853. doi:10.1001/jama.2013.170800
Implementation of infant rotavirus vaccination in 2006 has substantially reduced the burden of severe gastroenteritis among US children younger than 5 years. The role of rotavirus in adult gastroenteritis has been less well appreciated. Recent studies report rotavirus detection rates of 18% in emergency departments1 and 5% from February through May in hospitalized patients,2 and estimates of 81 000 emergency department visits3 and 18 000 hospitalizations4 in the United States annually. Whether indirect protection (due to reduced transmission of rotavirus) extends to adults remains unclear. Previous studies suggesting such indirect protection were limited to 1 postintroduction season5 or 1 hospital setting,6 so prudent interpretation was warranted. We assessed patterns of gastroenteritis hospitalizations among children aged 5 years or older and among adults before and after implementation of infant rotavirus immunization.
Rotavirus-coded and cause-unspecified gastroenteritis discharges from January 2000 through December 2010 were retrieved from a nationally representative database of hospital inpatient stays, the Nationwide Inpatient Sample, as previously described.5 Cause-unspecified discharges were examined because testing for rotavirus is infrequently performed in adults. We fitted time series regression models assuming a Poisson distribution of 2 separate outcomes: monthly counts of rotavirus-coded or cause-unspecified discharges. We estimated annual and monthly incidence rate ratios (RR) of the postvaccine years (2008, 2009, and 2010) separately and combined vs the prevaccine years (2000-2006), controlling for month, secular trends, and population size; 2007 was a transition year with limited coverage and was excluded. Separate models were fit for each of the 6 age groups. The study was exempt from institutional review board approval because deidentified aggregated data were used. Significance was assessed as a 2-sided P value of .05 using Stata version 12.0 (StataCorp).
Compared with prevaccine years, during 2008-2010, statistically significant reductions were observed in rotavirus-coded discharges by age group as follows: 0-4 years (RR, 0.20 [95% CI, 0.14-0.28]; P<.001), 5-14 years (RR, 0.30 [95% CI, 0.21-0.44]; P<.001), and 15-24 years (RR, 0.47 [95% CI, 0.24-0.94]; P = .03). Similarly, significant reductions were observed in cause-unspecified discharges by age group as follows: 0-4 years (RR, 0.58; 95% CI, 0.50-0.66), 5-14 years (RR, 0.70; 95% CI, 0.65-0.76), 15-24 years (RR, 0.89; 95% CI, 0.84-0.95), and 25-44 years (RR, 0.94; 95% CI, 0.90-0.98) (P<.001 for all; Table). Compared with prevaccine years, significant reductions in rotavirus-coded discharges occurred up to age 25 years in 2008, age 15 years in 2009, and across all age groups in 2010, with similar patterns for cause-unspecified discharges. Cause-unspecified reductions across all age groups and postvaccine years were focused in the late winter and early spring (Figure); in 2010, significant reductions were observed in March or April for all age groups.
The pattern of observed reductions in gastroenteritis discharges among unvaccinated older children and adults is consistent with indirect protection resulting from infant rotavirus vaccination. First, reductions occurred primarily in March and April, the peak months of rotavirus hospitalization prevaccine.5 Second, reductions mirrored the biennial epidemiology of childhood rotavirus during postvaccine years (ie, a large reduction in 2008, followed by a relatively smaller reduction in 2009, and the most pronounced reduction in 2010). Third, reductions persisted for 3 contiguous years and thus were unlikely due to year-to-year secular variations. In addition, reductions coincided with increasing vaccine coverage; significant reductions were observed across all ages in 2010, which is when the greatest decline in rotavirus hospitalizations among vaccine-eligible young children occurred.
Study limitations include the ecological design, lack of specificity of cause-unspecified discharges, and unknown specificity and infrequent use of rotavirus codes among adults. However, these limitations would only result in a bias if coding practices changed over time; broadly consistent results based on cause-unspecified and rotavirus-coded discharges suggest otherwise.
Based on the observed reductions, annual reductions in gastroenteritis discharges after introduction of rotavirus vaccine in the United States, particularly in the 5- to 44-year age group, are likely. These results point to the primacy of children in the transmission of rotavirus and illustrate how indirect benefits may amplify the effect of the US rotavirus vaccination program.
Corresponding Author: Paul A. Gastañaduy, MD, MPH, Division of Viral Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, Mailstop A-47, Atlanta, GA 30333 (firstname.lastname@example.org).
Author Contributions: Drs Gastañaduy and Lopman had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Gastañaduy, Parashar, Lopman.
Acquisition of data: Curns, Parashar, Lopman.
Analysis and interpretation of data: Gastañaduy, Curns, Parashar, Lopman.
Drafting of the manuscript: Gastañaduy, Parashar.
Critical revision of the manuscript for important intellectual content: Curns, Parashar, Lopman.
Statistical analysis: Gastañaduy, Curns, Lopman.
Administrative, technical, or material support: Gastañaduy, Curns, Parashar.
Study supervision: Parashar, Lopman.
Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention.