Superior relative efficacy of live attenuated influenza vaccine compared with inactivated influenza vaccine in young children with recurrent respiratory tract infections.
BACKGROUND
Young children have a high incidence of influenza and influenza-related complications. This study compared the efficacy and safety of cold-adapted influenza vaccine, trivalent (CAIV-T) with trivalent inactivated influenza vaccine (TIV) in young children with a history of recurrent respiratory tract infections (RTIs).


METHODS
Children 6 to 71 months of age were randomized to receive 2 doses of CAIV-T (n = 1101) or TIV (n = 1086), 35 +/- 7 days apart before the start of the 2002-2003 influenza season and were followed up for culture-confirmed influenza, effectiveness outcomes, reactogenicity, and adverse events.


RESULTS
Overall, 52.7% (95% confidence interval [CI] = 21.6%-72.2%) fewer cases of influenza caused by virus strains antigenically similar to vaccine were observed in CAIV-T than in TIV recipients. Greater relative efficacy for CAIV-T was observed for the antigenically similar A/H1N1 (100.0%; 95% CI = 42.3%-100.0%) and B (68.0%; 95% CI = 37.3%-84.8%) strains but not for the antigenically similar A/H3N2 strains (-97.1%; 95% CI = -540.2% to 31.5%). Relative to TIV, CAIV-T reduced the number of RTI-related healthcare provider visits by 8.9% (90% CI = 1.5%-15.8%) and missed days of school, kindergarten, or day care by 16.2% (90% CI = 10.4%-21.6%). Rhinitis and rhinorrhea, otitis media, and decreased appetite were the only events that were reported more frequently in CAIV-T subjects. There was no difference between groups in the incidence of wheezing after vaccination.


CONCLUSIONS
CAIV-T was well tolerated in these children with RTIs and demonstrated superior relative efficacy compared with TIV in preventing influenza illness.
Ashkenazi
Shai
S
Schneider Children's Medical Center, Petah-Tikva, Israel. sashkenazi@clalit.org.il
Vertruyen
Andre
A
Arístegui
Javier
J
Esposito
Susanna
S
McKeith
David Douglas
DD
Klemola
Timo
T
Biolek
Jiri
J
Kühr
Joachim
J
Bujnowski
Tadeusz
T
Desgrandchamps
Daniel
D
Cheng
Sheau-Mei
SM
Skinner
Jonathan
J
Gruber
William C
WC
Forrest
Bruce D
BD
D000281:Administration, Intranasal; D002675:Child, Preschool; D001068:Feeding and Eating Disorders / Q000209:etiology; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology; D053122:Influenza A Virus, H3N2 Subtype / Q000276:immunology; D009981:Influenza B virus / Q000276:immunology; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000009:adverse effects* / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology; D007273:Injections, Intramuscular; D008297:Male; D009975:Orthomyxoviridae / Q000145:classification / Q000302:isolation & purification; D010033:Otitis Media / Q000209:etiology; D012008:Recurrence; D012141:Respiratory Tract Infections / Q000150:complications; D012220:Rhinitis / Q000209:etiology; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000276:immunology
D007252:Influenza Vaccines; D014613:Vaccines, Attenuated; D015164:Vaccines, Inactivated