Effectiveness of live attenuated influenza vaccine and inactivated influenza vaccine in children 2-17 years of age in 2013-2014 in the United States.
BACKGROUND
A postmarketing observational study was initiated to evaluate quadrivalent live attenuated influenza vaccine (LAIV) effectiveness in children aged 2-17 years in the United States.


METHODS
Children and adolescents aged 2-17 years seeking outpatient care for febrile acute respiratory illness <5 days duration were enrolled at 4 geographically diverse sites during the 2013-2014 influenza season. Nasal swabs were tested for influenza using reverse transcription polymerase chain reaction. Vaccination status was documented from medical records or immunization registries. Children who received ≥1 dose of influenza vaccine ≥14 days before study visit were considered vaccinated. Vaccine effectiveness (VE) was estimated as 100×(1-adjusted odds ratio), where the odds of interest are the odds of vaccine exposure among influenza cases and test-negative controls.


RESULTS
In total, 1033 children and adolescents were included in the analysis. Influenza was detected in 14% (145/1033) of all children, with 74% (108/145) of the influenza cases due to A/H1N1pdm09 strains, 21% (31) to influenza B, and 4% (6) to influenza H3N2. LAIV did not show significant effectiveness against A/H1N1pdm09 (VE 13% [95% CI: -55 to 51]) but was effective against B/Yamagata strains (82% [95% CI: 12-96]). Inactivated influenza vaccine was effective against A/H1N1pdm09 (74% [95% CI: 50-86]) and B/Yamagata (70% [95% CI: 18-89]).


CONCLUSIONS
LAIV provided significant protection against B/Yamagata influenza but not against A/H1N1pdm09 in children aged 2-17 years in 2013-2014, resulting in a proposed change of the 2015-2016 formulation with a new and more heat-stable A/H1N1pdm09 LAIV strain.
['Caspard|Herve|H|', 'Gaglani|Manjusha|M|', 'Clipper|Lydia|L|', 'Belongia|Edward A|EA|', 'McLean|Huong Q|HQ|', 'Griffin|Marie R|MR|', 'Talbot|H Keipp|HK|', 'Poehling|Katherine A|KA|', 'Peters|Timothy R|TR|', 'Veney|Naomi|N|', 'Ambrose|Christopher S|CS|']
D000293:Adolescent D002648:Child D002675:Child, Preschool D005260:Female D006801:Humans D007252:Influenza Vaccines D007251:Influenza, Human D008297:Male D016896:Treatment Outcome D014481:United States D014613:Vaccines, Attenuated D015164:Vaccines, Inactivated
Quadrivalent live attenuated influenza vaccine LAIV Pediatrics