81. Effectiveness of Influenza Vaccine Against Life-threatening RT-PCR-Confirmed Influenza Illness in Children, 2010-2012
Session: Oral Abstract Session: Influenza Vaccine - Clinical Impact and Vaccine Response
Thursday, October 3, 2013: 9:00 AM
Room: The Moscone Center: 200-212
Background: Multiple studies have estimated influenza vaccine effectiveness in children for prevention of symptomatic and medically-attended influenza illness. This study is the first to examine protection conferred by influenza vaccine against life-threatening influenza in children.

Methods: Using a case-control design, we enrolled children 6 months to 17 years old during the 2010-11 and 2011-12 influenza seasons from 26 US pediatric intensive care units (PICUs) in the Pediatric Acute Lung Injury and Sepsis Investigators Network. Children admitted with acute severe respiratory illness who tested positive for influenza by reverse-transcription polymerase chain reaction were cases; children who tested negative were controls. A second control group included children (matched for comorbidities and geographic region) without a recent influenza hospitalization. Vaccine status was verified by medical record review.  Vaccine effectiveness (VE) was estimated with logistic regression models comparing fully vaccinated to unvaccinated children, adjusted for age, sex, onset date, medical conditions, and, for PICU subjects, PRISM score and days from illness onset to influenza testing.

Results: We enrolled 44 cases, 173 PICU controls, and 95 community controls with median ages of 51, 36, and 54 months, respectively. Fifteen (34%) cases, 89 (51%) PICU controls and 35 (37%) community controls had medical conditions that increase risk of influenza complications.  Over 20% of PICU subjects had ≥3 comorbidities. Eighteen percent of cases and 31% of PICU controls were fully vaccinated. Compared to unvaccinated children, children who were fully vaccinated were 74% (95% CI, 21 to 91%) less likely to be admitted to a PICU for influenza.  Fifty percent of community controls were fully vaccinated, yielding an adjusted VE of 77% (95% CI, 3 to 95%).  Receipt of one dose of vaccine among children for whom two doses were recommended was not associated with protection in either analysis.

Conclusion: During the 2010-11 and 2011-12 US influenza seasons, influenza vaccination was associated with a three-quarters reduction in the risk of life-threatening influenza illness among children.  Vaccine coverage was low, even among children with comorbidities that increase risk of severe influenza complications.

Jill Ferdinands, PhD, MSc1,2, Lauren Olsho, PhD3, Anna Agan, BA4, Niranjan Bhat, MD, MHS5, Mark Hall, MD6, Peter Mourani, MD7, Mark Thompson, PhD8, David K. Shay, MD, MPH1 and Adrienne Randolph, MD, MSc9, (1)Influenza Division, US Centers for Disease Control and Prevention, Atlanta, GA, (2)Battelle Memorial Institute, Atlanta, GA, (3)Abt Associates, Inc, Cambridge, MA, (4)Children's Hospital Boston, Boston, MA, (5)Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, (6)The Ohio State University/Nationwide Children's Hospital, Columbus, OH, (7)Critical Care Medicine, Children's Hospital Colorado, Aurora, CO, (8)Epidemiology and Prevention Branch, Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, (9)Department of Anesthesia, Perioperative and Pain Medicine, Children's Hospital Boston, Boston, MA

Disclosures:

J. Ferdinands, None

L. Olsho, None

A. Agan, None

N. Bhat, None

M. Hall, None

P. Mourani, None

M. Thompson, None

D. K. Shay, None

A. Randolph, None

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