Low allergic reaction rate seen in Gardasil study

The study, published today in the British Medical Journal, was based on vaccination data from Australia, which has had a nationwide program to vaccinate females ages 12 to 26 in schools since April 2007.

The study bolstered the case that the vaccine is relatively safe despite lingering concerns from some doctors and parents over its efficacy and safety.

The study, led by researchers at the Royal Children's Hospital in the state of Victoria, was prompted by media and medical reports of girls suffering allergic reactions after receiving a shot. Some patients reported dizzy spells, fainting or even temporary paralysis.

Similar concerns over Gardasil's safety have been raised in the U.S. even after the Food and Drug Administration in June 2006 approved the vaccine to protect against four strains of human papillomavirus that cause most cervical cancers and genital warts.

Some people do suffer serious reactions to vaccines, said Dr. Nicola P. Klein, co-director of Kaiser Permanente Vaccine Study Center in Oakland, who was not associated with the study. But it's not always easy to determine whether a reaction that occurred after someone is vaccinated was actually caused by the vaccine.

"If someone gets an injection and a few hours later there's some redness and pain at the injection, then that's pretty clear that it's from the injection," Klein said. But "many other things happen by chance alone, and [the person] just happened to get vaccinated beforehand."

Klein added that researchers have begun to look into whether teenagers might be more at risk of fainting after vaccination. Immunizations, a routine of early childhood, are relatively new for adolescents with the advent of a meningitis vaccine; a booster for tetanus, diphtheria and whooping cough; and now the HPV vaccine.

To confirm the possible allergic reactions to Gardasil, the Australian researchers collected vaccination data from the states of Victoria and South Australia.

Out of the 380,000 Gardasil doses administered, researchers found 35 reports of allergic reactions including hives, rashes and, in two cases, anaphylactic shock -- a sudden, severe reaction that can cause airways to tighten, among other symptoms.