Gardasil Safety: Questions and Answers

Experts Weigh In on Safety Concerns About HPV Vaccine Gardasil

Medically Reviewed by Louise Chang, MD on July 08, 2008
From the WebMD Archives

July 8, 2008 -- The vaccine Gardasil is making headlines -- but this time, it's about reported side effects and safety concerns.

The CDC and FDA have gotten 7,802 reports of adverse events in people who were vaccinated with Gardasil, the first cervical cancer vaccine, between June 8, 2006, and April 30, 2008. And two lawsuits have been filed, according to media reports, over Gardasil's safety.

Gardasil hasn't been proven responsible for any reported adverse events.

Is Gardasil safe? And what should parents do if they're concerned about letting their daughter get vaccinated with Gardasil?

WebMD contacted the CDC, Merck (the drug company that makes Gardasil), and an independent expert who's closely following Gardasil for their answers. But first, here's a quick recap of Gardasil's history.

(Have you considered giving your daughters the HPV vaccine? We're discussing it on WebMD's Parenting: Preteens and Teenagers board.)

About Gardasil

In June 2006, Gardasil hit the market as the first cervical cancer vaccine. Gardasil targets four strains of human papillomavirus (HPV) linked to many, but not all, cervical cancers and to genital warts.

Safety data reviewed by the FDA in approving Gardasil was based on about 11,000 people. Most side effects were mild or moderate reactions, such as pain or tenderness at the injection site.

In January 2007, the CDC added Gardasil to its routine childhood immunization schedule. The CDC recommended Gardasil, given in three doses, for all girls aged 11-12 and even for girls as young as 9, with catch-up doses for girls and women aged 13-26 who hadn't been vaccinated earlier.

More than 26 million doses of Gardasil have been distributed worldwide, including nearly 16 million in the U.S., according to Merck, which estimates that at least 8 million females in the U.S. have received their first dose of Gardasil.

Reported Adverse Events

The CDC and FDA monitor adverse events reported in people who get any vaccine, including Gardasil. All those reports go into the Vaccine Adverse Events Reporting System (VAERS).

The 7,802 adverse events reported to VAERS for Gardasil include 15 deaths and 31 reports of Guillain-Barre syndrome, a potentially paralyzing, life-threatening condition in which the body's immune system attacks part of the nervous system.

But the VAERS data doesn't tell the whole story, notes John Iskander, MD, MPH, the CDC's acting director of immunization safety.

Vaccine Not to Blame?

"VAERS receives unconfirmed reports of possible side effects" that may require further study, Iskander tells WebMD. That is, the reports don't show whether Gardasil caused the reported problems. Publicity tends to increase VAERS reports, and Gardasil has gotten a lot of publicity, says Iskander.

The serious reported events are about half of what's average for vaccines overall, according to the CDC.

The CDC hasn't been able to establish Gardasil's role in 10 of the deaths reported to VAERS; patient information wasn't available for the other five reported deaths.

"Nonserious events" such as pain at the injection site and fainting made up 93% of the reported Gardasil adverse events in the VAERS database, says Iskander.

He notes that teens are particularly likely to faint after any vaccination, not just with Gardasil. The CDC recommends that health care providers observe patients for 15 minutes after vaccination with any vaccine. As for the pain reports, Gardasil "does seem to cause a bit more discomfort to some people, compared to some of the other vaccines given to teenagers," says Iskander.

Merck, which continues to monitor Gardasil's adverse events, stresses the fact that adverse event reports don't amount to proof of cause and effect.

Different Opinions

Karen Smith-McCune, MD, PhD, associate professor of the department of obstetrics, gynecology, and reproductive science at the University of California, San Francisco, agrees that the VAERS data don't amount to proof.

But Smith-McCune, who has daughters in the age range for Gardasil vaccination, says she's waiting to see the final, published results from Gardasil's phase III clinical trials before she decides whether to let her daughters get vaccinated.

Merck presented those results to the CDC's Advisory Committee on Immunization Practices (ACIP) in February and plans to publish the findings later this year, Merck spokeswoman Amy Rose tells WebMD by email.

"That's great," says Smith-McCune. "Until we see the published, peer-reviewed final results from phase III trials, we don't have the gold standard of evidence for safety and efficacy."

Smith-McCune co-wrote an editorial in The New England Journal of Medicine in May 2008 recommending a cautious approach to the promising and apparently safe vaccine.

Iskander recommends that parents review the CDC's vaccine information statement on Gardasil and then make their decision about their daughters' vaccination.

"I think two years of post-licensure safety monitoring is really a good track record," says Iskander, who says he gives Gardasil in his clinical practice and abides by what patients decide about Gardasil vaccination. "Neither providers nor patients should be making decisions based on unfounded fears."

WebMD Health News



CDC: "Gardasil Vaccine Reports to VAERS."

News release, FDA.

John Iskander, MD, MPH, acting director for immunization safety, CDC.


WebMD Public Information from the U.S. National Institutes of Health: "What is Guillain-Barre Syndrome?"

Karen Smith-McCune, MD, PhD, associate professor of the department of obstetrics, gynecology, and reproductive science, University of California, San Francisco.

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