Anaphylaxis risk higher than normal with HPV vaccine, but still rare

NEW YORK (Reuters Health) - The quadrivalent human papillomavirus (HPV) vaccine (Gardasil) carries a higher risk of anaphylaxis than do other commonly administered vaccines, Australian researchers report. Still, the absolute risk of anaphylaxis with the HPV vaccine is very low.

The findings, which appear in the September 9th issue of the Canadian Medical Association Journal, come from a review of 12 suspected cases that arose after Australia began its National HPV Vaccination Program in 2007, providing free HPV vaccine to all females between the ages of 12 and 26.

Eight of the 12 cases were classified as anaphylaxis, Dr. Julia M. L. Brotherton, from The Children's Hospital at Westmead, and colleagues note. Four of the eight subjects had a negative skin-prick test for the HPV vaccine.

The authors calculate that just 2.6 cases of anaphylaxis will occur for every 100,000 doses of the HPV vaccine. Nonetheless, this is higher than the rate seen with other vaccines. For instance, with the conjugated meningococcal C vaccine, the anaphylaxis rate is 0.1 per 100,000 doses.

All of the cases of HPV vaccine-related anaphylaxis were successfully managed with no serious lasting effects.

"Anaphylaxis following HPV vaccination is a rare event, as defined by the World Health Organization, and it should not curtail population-based HPV vaccination programs," the authors conclude.

Editorialist Dr. Neal A. Halsey, from Johns Hopkins University in Baltimore, agrees, adding, "The risk of rare, but potentially serious, adverse events ... should not discourage the administration of this vaccine in school-based clinics, which are an effective means of reaching adolescents." Rather, vaccination initiatives should be prepared to rapidly detect and treat adverse reactions.

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