1351. Influenza Vaccine Effectiveness in the 20142015 Season for Children 2-17 Years by Vaccine Type: US Influenza Vaccine Effectiveness Network
Session: Oral Abstract Session: Vaccines for Seasonal and Avian Flu: Who Knew?
Saturday, October 10, 2015: 8:45 AM
Room: 5--AB
Background: Due to the lack of effectiveness of live attenuated influenza vaccine (LAIV) against pandemic H1N1 virus in children during 2013-14, the US Influenza Vaccine Effectiveness (VE) Network expanded enrollment of children during 2014-15 to determine influenza VE against medically attended acute respiratory illnesses (ARI) by vaccine type.

Methods: In a prospective, test-negative case-control study, patients >6 months of age with ARI of ≤7 days’ duration were enrolled at ambulatory care facilities in 5 sites nationally from 11/10/14 to 4/10/15.  Specimens were collected and tested for influenza by real-time reverse-transcriptase polymerase chain reaction (RT-PCR). Influenza vaccination status was based on medical record (EMR) or state immunization registry documentation, and if not available, by self-report. VE (1-adjusted odds ratio) was estimated by vaccine type with unvaccinated as the referent group in logistic regression adjusted for age, sex, site, days from illness onset to enrollment, calendar time (2-wk intervals), race/ethnicity and parent-rated general health.

Results: Among 9,506 enrollees, 1,976 (21%) were 2-8 years (younger) and 1,352 (14%) were 9-17 years (older).  In the younger group 428 (22%) were RT-PCR influenza positive, 653 (33%) had received ≥1 dose of 2014-15 inactivated influenza vaccine (IIV) and 332 (17%) had received ≥1 dose of LAIV.  In the older group, 394 (29%) were RT-PCR influenza positive, 353 (26%) had received ≥1 dose of 2014-15 IIV and 173 (13%) had received ≥1 dose of LAIV.  Among 822 influenza positives, 81% (664) were H3N2 (1 co-infected with B/Yamagata), 14% (115) were B Yamagata, 4% (31) were B Victoria. VE against H3N2 viruses among the younger group was -12% (-61, 22) for LAIV and 20% (-9, 41) for IIV; among the older group, VE was 3% (-58, 41) for LAIV and 14% (-21, 39) for IIV.  VE against the B Yamagata strain in the younger group was 71% (12, 90) for LAIV and 49% (-2, 75) for IIV; in the older group, VE was 72% (3, 92) for LAIV and 78% (45, 91) for IIV.  

Conclusion: VE estimates are consistent with a drifted H3N2 strain circulating in 2014-15.  There is no evidence that VE against drifted H3N2 for LAIV is higher than for IIV in 2-8 year-olds, supporting the 2015 ACIP decision for no preference among vaccine types in this age group.

Richard K. Zimmerman, MD MPH, FIDSA1, Brendan Flannery, PhD2, Alicia M. Fry, MD, MPH2, Swathi Thaker, PhD3, Jessie Clippard, MPH2, Michael Jackson, PhD, MPH4, Edward Belongia, MD5, Huong Mclean, MPH, PhD6, Manjusha Gaglani, MD (MBBS)7, Sarah Spencer, PhD3, Lisa A. Jackson, MD, MPH, FIDSA8, Lydia Clipper, RNC, BSN, CCRP9, Ryan E. Malosh, PhD10, Arnold Monto, MD, FIDSA11, Sean Saul, BS12 and Mary Patricia Nowalk, PhD1, (1)Family Medicine, University of Pittsburgh, Pittsburgh, PA, (2)Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, (3)Centers for Disease Control and Prevention, Atlanta, GA, (4)Group Health Research Institute, Seattle, WA, (5)Marshfield Clinic Research Foundation, Marshfield, WI, (6)Center for Clinical Epidemiology and Population Health, Marshfield Clinic Research Foundation, Marshfield, WI, (7)Baylor Scott & White Health, Texas A&M HSC COM, Temple, TX, (8)Center for Health Studies, Seattle, WA, (9)Scott and White Memorial Hospital, Temple, TX, (10)Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor, MI, (11)Univ. Michigan, Ann Arbor, MI, (12)University of Pittsburgh, Pittsburgh, PA

Disclosures:

R. K. Zimmerman, Merck & Co.: Grant Investigator , Research grant
Pfizer: Grant Investigator , Research grant
Sanofi Pasteur: Grant Investigator , Research grant

B. Flannery, None

A. M. Fry, None

S. Thaker, None

J. Clippard, None

M. Jackson, None

E. Belongia, Medimmune: Investigator , Research support

H. Mclean, MedImmune: Investigator , Research support

M. Gaglani, MedImmune: Investigator , Research support

S. Spencer, None

L. A. Jackson, None

L. Clipper, None

R. E. Malosh, None

A. Monto, None

S. Saul, Sanofi: Collaborator , Salary
Pfizer: Collaborator , Salary

M. P. Nowalk, Sanofi Pasteur: Grant Investigator , Research grant
Merck & Co.: Grant Investigator , Research grant
Pfizer: Grant Investigator , Research grant

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