How safe is the HPV vaccine?

An editorial in today’s issue of the Canadian Medical Association Journal (CMAJ) reports that the uptake of the human papillomavirus (HPV) vaccine in Ontario, which was made available to girls in Grade 8 last year through a school-based program, has been just 50 percent. In contrast, the uptake of the hepatitis B vaccine, through a similar school-based program, has been greater than 90 percent. So what accounts for this difference? After all, both vaccines are proven to protect against serious sexually transmitted infections. In the case of HPV, infection early in life may cause cervical cancer much later on.

Part of the explanation for why parents are opting not to have their daughters vaccinated is concern over the vaccine’s safety. Although all vaccines are tested for effectiveness and safety, such trials often have too few participants to detect rare but serious adverse effects, says the editorial. But once a vaccine is introduced to the public, researchers can get a more complete picture of its side effects. The implementation of a National HPV Vaccination Program in Australia in 2007 allowed health researchers to take a closer look. Now, a new study published in the same issue of the journal, provides evidence that the HPV vaccine really is safe.

Dr. Julia Brotherton and colleagues tracked adverse effects in response to 260 000 doses of the vaccine (provided to women age 12 to 26 years old across Australia) and found that it very rarely caused cases of anaphylaxis (a severe allergic reaction) and no cases of anaphylactic shock. The rate of anaphylaxis (2.6 cases per 100,000 doses) was higher than expected (for example, the rate was just 0.1 per 100,000 doses with the meningococcal C vaccination), but the researchers conclude that the over all rates were low, and the vaccine had no negative long-term consequences on the health of its recipients.

"These data should provide reassurance to parents and potential recipients who have called for more evidence of the vaccine’s safety," write the CMAJ’s editors. "Delaying immunization until a young woman is sexually active may seem a credible alternative, but it is not. "

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