Intradermal influenza vaccine administered using a new microinjection system produces superior immunogenicity in elderly adults: a randomized controlled trial.
BACKGROUND
Enhanced influenza vaccines are needed to provide improved protection for elderly individuals. The intradermal vaccination route was hypothesized to provide immunogenicity superior to that provided by the intramuscular vaccination route.


METHODS
In a multicenter, randomized study, 1107 volunteers >60 years of age received intradermal trivalent inactivated influenza vaccine containing 15 or 21 microg of hemagglutinin per strain or intramuscular control vaccine. Intradermal vaccines used a novel microinjection system designed to ensure easy, convenient, consistent vaccination. The primary end points of the study were the strain-specific hemagglutination inhibition geometric mean titers (GMTs) noted 21 days after vaccination. Groups were compared using noninferiority and superiority analyses.


RESULTS
For each strain, the GMTs noted in association with each intradermal vaccine were superior to those noted with the intramuscular control (adjusted P< .0001). Seroprotection rates, seroconversion rates, and mean titer increases were also superior for intradermally administered vaccine in all but one of the analyses undertaken. Systemic reactogenicity was comparable between routes. Local injection site reactions, particularly erythema but not pain, were more commonly associated with intradermal vaccination.


CONCLUSIONS
For the first time, the intradermal vaccination route has been used to elicit immune responses significantly superior to those noted in association with the conventional intramuscular vaccination route. This was done using an easy-to-use, reliable microinjection system. This superior response is expected to enhance annual protection against influenza in this vulnerable population.


BACKGROUND
Clinicaltrials.gov registry number: NCT00296829.
Holland
David
D
Centre for Clinical Research and Effective Practice, Middlemore Hospital, Auckland, New Zealand. holland@middlemore.co.nz
Booy
Robert
R
De Looze
Ferdinandus
F
Eizenberg
Peter
P
McDonald
James
J
Karrasch
Jeff
J
McKeirnan
Maureen
M
Salem
Hatem
H
Mills
Graham
G
Reid
Jim
J
Weber
Françoise
F
Saville
Melanie
M
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000276:immunology*; D004306:Dose-Response Relationship, Immunologic; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology*; D007251:Influenza, Human / Q000276:immunology* / Q000517:prevention & control; D007271:Injections, Intradermal / Q000295:instrumentation; D008297:Male; D008845:Microinjections; D008875:Middle Aged; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000009:adverse effects / Q000276:immunology
D007252:Influenza Vaccines; D015164:Vaccines, Inactivated