Follow-up study clears cancer vaccine (Gardasil)

depakid

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Sat Dec-06-08 05:38 PM
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Follow-up study clears cancer vaccine (Gardasil)

Edited on Sat Dec-06-08 05:42 PM by depakid

AUSTRALIA'S breakthrough cancer vaccine has been given the all-clear in a follow-up study of schoolgirls who fell ill after being injected with Gardasil.

The study took in 25 young women who were reported to immunisation authorities as suffering from a "suspected hypersensitivity" reaction during the national roll-out of the cervical cancer vaccine.

After a range of skin-prick and injection tests, only one young woman went on to develop a case of possibly unrelated hives when re-exposed to the vaccine.

"Only three of the 25 evaluated schoolgirls had probable hypersensitivity to the quadrivalent human papilloma virus vaccine after 380,000 doses had been administered in schools," the research paper, published in the British Medical Journal, also concludes.

"Our data suggest that true hypersensitivity to the ... vaccine is uncommon and that suspected hypersensitivity reactions such as urticaria (hives) are often idiosyncratic."

The study was conducted by Sharon Choo, attached to the Department of Allergy and Immunology at Melbourne's Royal Children's Hospital, and colleagues.

Gardasil, developed by the 2006 Australian of the Year, scientist Ian Frazer, provides protection against 70 per cent of cervical cancers by blocking two strains of the sexually-transmitted human papilloma virus.

The national vaccination of females aged 12 to 26 began in April last year, when it also sparked media reports of fainting and dizzy spells, even temporary paralysis, among some schoolgirls.

The research paper also notes that such reactions were typical during any mass vaccination effort, regardless of what was being injected. "One study estimated that if 80 per cent of eligible US adolescent females were to receive a saline injection ... three per 100,000 adolescents would require emergency care for asthma or allergy within 24 hours of vaccination," the paper says.

http://www.theaustralian.news.com.au/story/0,25197,24748394-23289,00.html

Clinical information from Medscape:

This finding is in contrast to what was reported a few months ago (CMAJ. 2008;179:525-533), when Australian researchers said the rate of anaphylaxis after HPV vaccine was higher than with other vaccines, as reported by at the time by Medscape Oncology.

Australia has a national program of HPV immunization, launched in April 2007, which provides the quadrivalent HPV vaccine Gardasil (Merck & Co) free to all women between 12 and 26 years of age. Both of the reports of hypersensitivity reactions are based on data collected in the school-based part of the program.

Detailed Examination of Cases

The earlier report concluded that the rate of anaphylaxis with the HPV vaccine was significantly higher than for other vaccines administered in school programs. From the 269,680 HPV vaccine doses administered in schools, 7 cases of anaphylaxis were identified, which represents an incidence rate of 2.6 per 100,000 doses (95% confidence interval , 1.0 - 5.3 per 100,000), the researchers reported. In comparison, they noted that the rate of identified anaphylaxis was 0.1 per 100,000 doses (95% CI, 0.003 - 0.700) for conjugated meningococcal C vaccination in a 2003 school-based program.

That report may have been an overestimate, however. The current study concludes that "true hypersensitivity" to the HPV vaccine is uncommon, and a detailed examination of case reports found only 2 cases of anaphylaxis after more than 380,000 vaccine doses.

The 2 studies come from 2 different sets of researchers, although 1 author contributed to both papers. In the latest study, Liew Woei Kang MD, from the Royal Children's Hospital, in Victoria, Australia, and colleagues followed 35 cases of suspected hypersensitivity after more than 380,000 doses had been administered in schools, although only 25 of the 35 schoolgirls (71%) agreed to undergo further evaluation.

Among these 25 cases, further testing and evaluation led the researchers to conclude that only 3 had "probable hypersensitivity" to the vaccine, and 1 had "possible hypersensitivity." Another 4 schoolgirls had reactions that were "unlikely" to be hypersensitivity, and the remaining 17 girls had reactions that were not hypersensitivity, they conclude.

Among the 3 reactions that were judged to be "probable hypersensitivity, "1 girl had a positive intradermal test that was consistent with immunoglobulin E-mediated hypersensitivity. Another case was considered to be anaphylaxis with symptoms of urticaria, angioedema, laryngeal edema, and palpitations, and the third case was considered to be a hoarse voice. One occurred after the second dose of vaccine, the other after the third dose.

"Our study describes 2 cases of anaphylaxis after 380,000 doses of the quadrivalent vaccine had been administered," the researchers conclude.

More info at link: http://www.medscape.com/viewarticle/584651