Reactions such as hives called 'idiosyncratic,' study finds
THURSDAY, Dec. 4 (HealthDay News) -- Reactions to the vaccine designed to protect against cervical cancer are rare, and young women can tolerate subsequent doses.
That's the assessment of Australian researchers who analyzed data after more than 380,000 doses of the Gardasil vaccine were given to girls in secondary schools beginning in April 2007.
Gardasil protects against four types of human papillomavirus (HPV) that increase the risk of cervical cancer. Some ingredients of the vaccine, such as aluminum salts and yeasts, have previously been associated with hypersensitivity reactions.
The Australian researchers identified 35 schoolgirls with suspected hypersensitivity reactions, including hives, generalized rash, swelling of subcutaneous tissues (angioedema), and severe allergic reaction (anaphylaxis).
Twenty-five of the girls agreed to be referred to pediatric allergy centers for further evaluation. This included a detailed account of their reactions, such as previous doses of the vaccine, time and severity of reaction, and previous clinical history. Skin tests of HPV vaccines were conducted, and vaccine challenges were administered intramuscularly. The girls were followed-up by telephone one week after the subsequent dose, and any adverse events were noted, the researchers said.
Nineteen girls had skin testing of the Gardasil vaccine, and all were negative. Seventeen of 18 girls later "challenged" with the vaccine tolerated further doses. One girl reported a limited case of hives four hours after receiving the vaccine. Only three of the 25 evaluated girls had probable hypersensitivity to the vaccine, and the researchers concluded that true hypersensitivity is rare.
They noted that suspected hypersensitivity reactions such as hives are often "idiosyncratic" and don't increase the risk of adverse reactions in subsequent vaccinations. Girls with suspected hypersensitivity to the vaccine should be evaluated before receiving further doses, said the researchers, who called for more research into the mechanisms of hypersensitivity to the vaccine.
The study was published online Dec. 3 in the BMJ.
The U.S. National Cancer Institute has more about HPV vaccines.
-- Robert Preidt
SOURCE: British Medical Journal, news release, Dec. 3, 2008
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