Australians report higher-than-expected rate of allergic reaction to HPV shot

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By Helen Branswell
THE CANADIAN PRESS

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TORONTO - Australian researchers have observed a higher-than-expected rate of a severe allergic reaction called anaphylaxis in young women who have received the HPV or human papillomavirus vaccine, Gardasil.

Anaphylactic reactions are typically seen in about one case in one million vaccinations for many vaccines. But during the HPV vaccination program in New South Wales in 2007, anaphylaxis was reported at a rate of about 2.6 cases per 100,000 vaccinations, the researchers said this week in the Canadian Medical Association Journal.

The lead author of the study said she and her colleagues could not determine what was behind the higher-than-normal rate of allergic reactions. But Dr. Julia Brotherton insisted the findings shouldn't deter parents from getting their daughters vaccinated.

"This is still vanishingly rare. And it's easily treated if it's recognized rapidly," Brotherton said from Sydney, where she is a public health physician with Australia's National Centre for Immunization Research and Surveillance.

Anaphylaxis is an allergic reaction involving hives or an itchy rash, a quickening heart beat and wheezing or breathing difficulties. The condition sets in rapidly and is generally triggered by exposure to a food or drug to which a person is allergic, or the sting of insect.

All of the girls recovered after being treated with epinephrine, also known as adrenaline. None experienced the most serious -- and life threatening -- form of the condition, anaphylactic shock.

Merck Frosst Canada -- the Canadian subsidiary of Merck & Co., which makes Gardasil -- said in a statement that the safety profile of the vaccine "remains excellent."

The elevated rate of anaphylaxis seen in New South Wales hasn't been mirrored in North America, public health officials said.

"We've seen no confirmed reports of anaphylaxis in Canada," said Dr. David Butler-Jones, Canada's chief public health officer.

"The rates are still exceedingly low," he said of the Australian rate. "It's still a very good and safe vaccine."

Side-effects reported in Canada are similar to those reported in the U.S., Butler-Jones said -- things like acute tenderness at the site of the injection and some cases of fainting.

Dr. John Iskander, acting director for immunization safety at the Centers for Disease Control in Atlanta, said that the U.S. reporting system for adverse reactions to vaccinations isn't picking up evidence of elevated rates of anaphylaxis among American girls who have received the HPV vaccine.

With more than 16 million doses of the vaccine administered in the U.S., Iskander said, the rate of anaphylaxis is what one would expect -- about one case per million doses.

But Iskander said a study is underway to look more closely for adverse reactions to the vaccine.

And Dr. Neal Halsey, of the Institute of Vaccine Safety at the Johns Hopkins Bloomberg School of Public Health, said it will be critical to try to find out what was behind the elevated anaphylaxis rates in New South Wales. "We need to look at that very carefully and try to figure out exactly what was happening."

Halsey and others also noted the phenomenon points to the importance of taking the necessary precautions when administering vaccines -- observing people who have been vaccinated for 15 minutes after they get a shot to ensure they are OK and having epinephrine on hand in case it is needed.

Gardasil, currently the only licensed HPV vaccine, protects against infection by two strains of HPV that are responsible for about 70 per cent of all cervical cancers as well as two strains that cause genital warts.

Roughly 1,300 women will be diagnosed with cervical cancer in Canada this year and 380 will die from the disease.

Despite the anticipated appeal of what has been touted as the first vaccine to prevent a form of cancer, there has been a decidedly mixed response to the HPV vaccine since it hit the market in the past couple of years.