Efficacy of inactivated split-virus influenza vaccine against culture-confirmed influenza in healthy adults: a prospective, randomized, placebo-controlled trial.
BACKGROUND
A new trivalent inactivated split-virus influenza vaccine (TIV) was recently introduced in the United States. We assessed the efficacy of TIV against culture-confirmed influenza A and/or B.


METHODS
In this double-blind trial conducted from September 2006 to May 2007 in the Czech Republic and Finland, participants aged 18-64 years were randomized to receive 1 dose of TIV (n = 5103) or placebo (n = 2549). Influenza-like illnesses (ILI) (defined as at least 1 systemic symptom [fever {oral temperature, > or = 37.8 degrees C} and/or myalgia] and at least 1 respiratory symptom [cough and/or sore throat]) were identified by both active (biweekly phone contact) and passive surveillance. Nasal and throat swab specimens were collected for viral culture.


RESULTS
The attack rate for culture-confirmed ILI was 3.2% in the placebo group, with most strains identified as influenza A (all except 1 were H3N2) matching the vaccine strain. There were 6 cases of influenza B, all of which were of a different lineage (Yamagata) than the vaccine strain. Vaccine efficacy against culture-confirmed influenza A and/or B due to strains antigenically matched to the vaccine was 66.9% (95% confidence interval [CI], 51.9%-77.4%; P < .001) and to any strain was 61.6% (95% CI, 46.0%-72.8%; P < .001).


CONCLUSIONS
TIV is efficacious against culture-confirmed influenza in healthy adults.


BACKGROUND
ClinicalTrials.gov identifier: NCT00363870.
Beran
Jiri
J
The Vaccination and Travel Medicine Center, University Hospital, 500 03 Hradec Kralove, Czech Republic. jiri.beran@vakcinace.cz
Vesikari
Timo
T
Wertzova
Veronika
V
Karvonen
Aino
A
Honegr
Karel
K
Lindblad
Niklas
N
Van Belle
Pascale
P
Peeters
Mathieu
M
Innis
Bruce L
BL
Devaster
Jeanne-Marie
JM
D000328:Adult; D018153:Czech Republic; D004311:Double-Blind Method; D005260:Female; D005387:Finland; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology / Q000302:isolation & purification; D053122:Influenza A Virus, H3N2 Subtype / Q000276:immunology / Q000302:isolation & purification; D009981:Influenza B virus / Q000276:immunology / Q000302:isolation & purification; D007252:Influenza Vaccines / Q000276:immunology*; D007251:Influenza, Human / Q000517:prevention & control* / Q000821:virology; D008297:Male; D008875:Middle Aged; D010919:Placebos / Q000008:administration & dosage; D011446:Prospective Studies; D015164:Vaccines, Inactivated / Q000276:immunology; D022223:Vaccines, Subunit / Q000276:immunology; D055815:Young Adult
D007252:Influenza Vaccines; D010919:Placebos; D015164:Vaccines, Inactivated; D022223:Vaccines, Subunit