1352. Multicenter Study of Live Attenuated Influenza Vaccine Effectiveness in Children, 2014-15
Session: Oral Abstract Session: Vaccines for Seasonal and Avian Flu: Who Knew?
Saturday, October 10, 2015: 9:00 AM
Room: 5--AB

Background: The effectiveness of quadrivalent live attenuated influenza vaccine (LAIV4) in children is monitored during each influenza season. The purpose of this study is to determine the vaccine effectiveness of LAIV4 in children in influenza season 2014-15 versus no vaccine and trivalent or quadrivalent inactivated influenza vaccines (IIV3/4).

Methods: Children 217 years old seeking outpatient care for febrile acute respiratory illness <5 days duration were enrolled at 4 sites (NC, TN, TX, WI) during the influenza season. Nasal swabs were tested for influenza by reverse transcription polymerase chain reaction (RT-PCR). Vaccination status was documented from medical records or immunization registries; children who received ≥1 dose at least 14 days before illness onset were considered vaccinated. Effectiveness was estimated as 100 (1 adjusted odds ratio) in influenza cases vs test-negative controls.

Results: The analysis included 1,671 children. The mean age was 7.7 (SD 4.1) years and 532 (52%) were male. RT-PCR was positive for influenza in 440 children: 326 tested positive for A/H3N2 and 114 for a B strain. Vaccine effectiveness by strain is described in the table.

Influenza strain

No vaccination, n
n=892

LAIV4, n
n=244

IIV3/4, n
n=535

LAIV Effectiveness vs no vaccine*
% (95% CI)

LAIV Effectiveness vs IIV*
% (95% CI)

Cases

Controls

Cases

Controls

Cases

Controls

A/H3N2

202

614

47

193

77

424

22 (-17 to 48)

-17 (-83 to 25)

Vaccine-like

6

1

4

36 (-467 to 93)

58 (-291 to 96)

Any B

76

4

34

86 (62 to 95)

80 (41 to 93)

B/Yamagata

53

4

26

81 (45 to 93)

73 (21 to 91)

B/Victoria

14

0

6

100 (NE to 100)

100 (NE to 100)

B undetermined

9

0

2

 

 

Any influenza

278

51

111

45 (21 to 61)

16 (-25 to 43)

NE = not evaluable.
*Adjusted for site and month of enrollment, age group, and number of outpatient visits in the last 6 months.

Conclusion: LAIV effectiveness against B strains was significant versus no vaccine (86% [62 to 95]) or IIV (80% [41 to 93]), but LAIV effectiveness against A/H3N2 strains was not. Almost all circulating A/H3N2 strains were antigenically different from the vaccine strain.

Herve Caspard, MD, ScD1, Manjusha Gaglani, MD (MBBS)2, Lydia Clipper, RNC, BSN, CCRP3, Edward a. Belongia, MD4, Huong Q. Mclean, PhD, MPH4, Marie R. Griffin, MD, MPH5, H. Keipp Talbot, MD, FIDSA6, Katherine a. Poehling, MD, MPH7, Timothy R. Peters, MD7 and Christopher S. Ambrose, MD8, (1)MedImmune, Gaithersburg, MD, (2)Baylor Scott & White Health, Texas A&M HSC COM, Temple, TX, (3)Scott and White Memorial Hospital, Temple, TX, (4)Marshfield Clinic Research Foundation, Marshfield, WI, (5)Vanderbilt University Medical Center, South Nashville, TN, (6)Vanderbilt University Medical Center, Nashville, TN, (7)Wake Forest School of Medicine, Winston-Salem, NC, (8)AstraZeneca, Gaithersburg, MD

Disclosures:

H. Caspard, MedImmune: Employee , Salary

M. Gaglani, MedImmune: Investigator , Research support

L. Clipper, None

E. A. Belongia, MedImmune: Investigator , Research grant

H. Q. Mclean, MedImmune: Investigator , Research support

M. R. Griffin, MedImmune: Grant Investigator , Research grant and Research support

H. K. Talbot, MedImmune: Investigator , Research support
Sanofi Pasteur: Investigator , Research support
Gilead: Investigator , Research support
Teva: Scientific Advisor , Consulting fee
VaxInnate: Scientific Advisor , Consulting fee

K. A. Poehling, MedImmune: Investigator , Research support

T. R. Peters, MedImmune: Investigator , Research support

C. S. Ambrose, AstraZeneca: Employee and Shareholder , Salary

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