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| |  Skin-Prick Testing for Military-Significant Vaccines Effective, Dose Reactions May Be Delayed: Presented at ACAAI By Carole VanSickle Ellis PHOENIX, Ariz -- November 15, 2010 -- Irritant dose reactions may be encountered between 8% and 25% of the time during skin-prick testing for military-significant vaccines such as anthrax, Japanese encephalitis (JEV), meningococcal, and typhoid, researchers noted here at the 2010 Annual Meeting of the American College of Allergy, Asthma and Immunology (ACAAI). Delayed reactions to these skin-prick tests are not uncommon, noted Kimberly S. Johnson, MD, Willford Hall Medical Centre, Lackland Air Force Base, San Antonio, Texas, speaking here on November 13. There are, however, rarely false-positives in these tests, which help military allergists determine how an individual will tolerate a vaccine, she added. Dr. Johnson and her research team worked with 12 patients who had met safety-screening standards and were enrolled for skin-prick testing at full-strength concentration. The patients were tested using intradermal skin-testing procedures at full strength, 1:100, and 1:10 concentrations. They were also monitored for immediate, persistent, and delayed reactions at 24 to 72 hours and at 7 days after the tests were performed. “No immediate irritant reactions occurred during skin-prick testing,” explained Dr. Johnson, adding that patients only experienced irritant dose reactions with full-strength vaccine intradermal testing, and there were no reactions at the 1:100 and 1:10 concentrations. Numerous delayed reactions (34), however, occurred after the 24-hour postprocedure check and lasted more than 7 days, but resolved within 21 days. These delayed reactions were associated with erythema and pruritus in 2 more severe cases in reaction to a full-strength anthrax prick and a full-strength meningococcal prick, respectively. Hyperpigmentation often took several days to fade away entirely, but “none of the delayed reactions caused any permanent skin injury,” reported Dr. Johnson. She noted that 4 of the 12 subjects accounted for all 5 of the full-strength irritant dose responses. The team concluded that allergists should feel confident when using skin-prick testing for the target vaccines at full strength concentration, and should not generally expect to deal with an irritant dose reaction. Furthermore, immediate irritant dose responses from 1:100 and 1:10 concentrations should also not complicate interpretation of results since false-positive results are rarely encountered, said Dr. Johnson. She emphasised, however, that, given the high number of delayed reactions, “patients undergoing this type of testing should be warned of this phenomenon.” [Presentation title: Nonirritant Skin Test Concentrations of Military Significant Vaccines. Abstract P28]
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