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Low Doses of Intradermal Flu Vaccine Perform Well

Intradermal flu vaccine could prove to be useful in the event of future shortages.

Because the skin contains large numbers of antigen-presenting cells, intradermal vaccination often elicits antibody response more efficiently than does intramuscular vaccination. In two open-label, industry-sponsored studies, researchers explored serologic responses to low doses of intradermal influenza vaccine.

One research group randomized 100 healthy young adults to receive either the standard IM dose of the 2003-2004 trivalent influenza vaccine, or 20% of the standard dose administered intradermally. Although titers to individual vaccine components varied somewhat by administration route, seroconversion and seroprotection rates at 3 weeks after vaccination were similar in the two groups.

Another group randomized 238 healthy adults (45% older than 60) to receive either the standard IM dose of the 2003-2004 flu vaccine, or an intradermal dose of the vaccine, slightly reconfigured to 40% of standard composition. Subjects who were younger than 60 had similar responses to both routes. Among the older group, responses were less vigorous overall, and, for one antigen, response to intradermal vaccination was significantly less than response to intramuscular vaccination. Still, seroprotection rates exceeded 90% against all antigens in both age groups.

Local reactions to intradermal vaccination were common but short-lived in both studies.

Comment: Although the findings need clinical confirmation, these studies join others in suggesting that intradermal administration of the flu vaccine could stretch a limited supply -- a useful take-home message in the event of future shortages. Editorialists also note that exploiting the immune potency of the dermis could enhance vaccine immunogenicity in populations in which the efficacy of IM vaccination has been disappointing (e.g., elders).

— Abigail Zuger, MD

Published in Journal Watch General Medicine December 14, 2004

Citation(s):

Kenney RT et al. Dose sparing with intradermal injection of influenza vaccine. N Engl J Med 2004 Nov 25; 351:2295-301.

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• Medline abstract (Free)

Belshe RB et al. Serum antibody responses after intradermal vaccination against influenza. N Engl J Med 2004 Nov 25; 351:2286-94.

• Original article (Subscription may be required)
• Medline abstract (Free)

La Montagne JR and Fauci AS. Intradermal influenza vaccination -- Can less be more? N Engl J Med 2004 Nov 25; 351:2330-2.

• Original article (Subscription may be required)
• Medline abstract (Free)