25477 Safety and Immunogenicity of Intradermal Influenza Vaccine Compared to Intramuscular Influenza Vaccine When Used to Revaccinate Healthy Adult Subjects Aged 18 to 64 Years

Tuesday, March 29, 2011
Columbia Hall

Background: Previously, Fluzone® Intradermal (ID) Vaccine (9 µg hemagglutinin [HA]/strain delivered via the BD Soluvia™ Microinjection System) was as immunogenic and safe as Fluzone vaccine (15 µg HA/strain) given intramuscularly (IM) in healthy adults 18-64 years old.

Objectives: To evaluate the safety and immunogenicity of revaccination with ID vaccine during a 2nd year follow-up vaccination protocol.

Methods:  Subjects (N=1250) who had received ID or IM vaccine in the first study year were randomly assigned prior to the influenza season of the following year (2009) into 1 of 4 groups: subjects vaccinated with ID were revaccinated with ID (ID/ID, N=505) or IM (ID/IM, N=251) vaccine; subjects vaccinated with IM were revaccinated with IM (IM/IM, N=237) or ID (IM/ID, N=246) vaccine. Local and systemic reactions were recorded and immunogenicity measured at day 28 by hemagglutination inhibition (HAI) assay.

Results: After revaccination, rates of systemic reactions (headache, malaise, myalgia, fever) were comparable in all 4 groups, but local injection-site reactions (erythema, swelling, induration, pruritus, but not pain) were more frequent after receipt of ID than IM vaccine. Safety profiles were similar between the 2 groups revaccinated with ID (ID/ID and IM/ID) and between the 2 groups revaccinated with IM (ID/IM and IM/IM). Most solicited reactions in all groups were Grade 1 or 2 in intensity and resolved in 3-7 days. There were no serious adverse events related to vaccination. HAI antibody responses to A/H1N1, A/H3N2, and B were similar among all groups by geometric mean titers, and rates of seroconversion and seroprotection.  

Conclusions:  Revaccination with intradermal influenza vaccine was well tolerated regardless of the previous year’s vaccination regimen. Antibody responses to all 3 virus strains were comparable after ID and IM revaccination. Fluzone Intradermal Vaccine with reduced HA dose appears to be a viable alternative to standard influenza vaccines administered intramuscularly.