Immunogenicity and safety of intradermal influenza immunization at a reduced dose in healthy children.
OBJECTIVE
We conducted this study to test the hypothesis that intradermal influenza vaccination at one fifth of a standard dose elicits comparable immunogenicity to full-dose intramuscular vaccination in children.


METHODS
We conducted a randomized, open-label study in 112 healthy children aged 3 to <18 years to compare the immunogenicity and safety of intradermal vaccination at one fifth of a dose with standard intramuscular vaccination. Analyses of hemagglutination inhibition antibody titers to each antigen in each group included geometric mean titers before and 21 days after vaccination, fold increase in geometric mean titers after vaccination, seroprotection rate, and seroconversion rate.


RESULTS
The mean age of the subjects was 10.11 +/- 4.04 years in the intradermal vaccination group and 10.57 +/- 3.91 years in the intramuscular group. Intradermal vaccination was safe. Induration and mild erythema at the injection site were reported at 25% and 57%, respectively, in the intradermal group. Fold increase of geometric mean titers against influenza A/Caledonia was robust in both groups (11.1-fold and 12.9-fold increase in the intramuscular and intradermal groups, respectively), whereas that for B/Shandong was more modest (4.3-4.4). Both approaches elicited very high geometric mean titers against influenza A/Panama: 1360.5 and 893.9 for the intramuscular and intradermal groups, respectively, but because the prevaccination antibody titers were high, the fold increase of geometric mean titers was only 4.5 and 2.6, respectively.


CONCLUSIONS
The immunogenicity of one fifth of a dose of influenza vaccine delivered by the intradermal route is comparable to the standard-dose intramuscular vaccination in children as young as 3 years of age.
Chiu
Susan S
SS
Department of Pediatrics and Adolescent Medicine, University of Hong Kong, Hong Kong, China. ssschiu@hkucc.hku.hk
Peiris
J S Malik
JS
Chan
Kwok H
KH
Wong
Wilfred Hing Sang
WH
Lau
Yu Lung
YL
D000293:Adolescent; D000914:Antibodies, Viral / Q000096:biosynthesis* / Q000097:blood; D002648:Child; D002675:Child, Preschool; D004890:Erythema / Q000453:epidemiology / Q000276:immunology; D005260:Female; D006801:Humans; D007252:Influenza Vaccines / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology*; D007271:Injections, Intradermal; D007273:Injections, Intramuscular; D008297:Male; D010146:Pain / Q000453:epidemiology / Q000276:immunology; D014611:Vaccination / Q000009:adverse effects*
D000914:Antibodies, Viral; D007252:Influenza Vaccines