The latest news about the safety of the HPV vaccine is certainly reassuring. The Centers for Disease Control and Prevention announced Wednesday that the Gardasil shot against the cervical-cancer causing human papillomavirus is "safe to use and effective in preventing four types of HPV." That's based on their database surveillance system—called the Vaccine Safety Datalink—which reviewed the medical records of 190,000 girls and young women who have received the shot. This review didn't turn up any increased risk of blood clots, seizures, paralysis, strokes, fainting, or life-threatening allergic reactions. "To date, we have not seen a causal relationship between vaccines and adverse reactions," says CDC spokesperson Curtis Allen.
So does "safe" mean risk free? "You'll never get us to say this vaccine is absolutely safe," Allen responded. After all, the Vaccine Safety Datalink isn't large enough to pick up rare events like anaphylaxis, which occurs in 1 out of every 2 million of those who get vaccines. Indeed, the Datalink, says Allen, didn't detect a single case of anaphylaxis. Nor did it detect an increase in fainting, which even manufacturer Merck admits "has been reported following vaccination with Gardasil." (For this reason, teens who receive the shot are supposed to wait 15 minutes before leaving the doctor's office.) Merck's clinical trial involving more than 25,000 participants has shown an increased frequency of fever, nausea, and dizziness as well as pain, swelling, bruising, and rashes at the injection site compared with those who received a placebo shot.
Those are mild reactions when weighed against the protection young women get against cervical cancer and genital warts. The question is: Does the vaccine pose any real danger even if only in rare cases? University of California-Berkeley Prof. Phillip Tetlock has been researching this question for months after his 13-year-old daughter, Jenny, developed severe paralysis soon after getting Gardasil. It turns out Jenny probably has juvenile amyotrophic lateral sclerosis, the fatal disease that killed Lou Gehrig. Whitney Baird, 22, died in August from this disease, just 13 months after receiving Gardasil. Both were healthy before getting the shot. Yet the condition is extraordinarily rare, affecting just 1 in every 2 million people. John Iskander, the CDC's acting director for the immunization safety office, tells me that both of these cases have been reviewed by CDC researchers and that "in their expert judgment, they didn't feel that vaccines were the likely trigger."
Barbara Shapiro, an associate professor of neurology at Case Western Reserve University School of Medicine who has reviewed both Jenny and Whitney's medical records, says it's impossible to know at this point whether Gardasil was somehow to blame for their tragic illnesses. "These cases are somewhat alarming but certainly don't prove that Gardasil causes ALS," she says. But they have raised red flags, considering the rarity of juvenile ALS and certain similarities between Whitney and Jenny: They both had autoimmune skin disorders and developmental delays as young children, and both rapidly deteriorated into full-blown paralysis, which Shapiro says is unusual for juvenile ALS. She adds, however, that she doesn't know how Gardasil fits into all of this—if at all. One possibility is that the vaccination somehow triggered a reaction that started killing off nerve cells called motor neurons. Jenny was found to have a mutation in a motor neuron gene, Shapiro says, which could have predisposed her to having a reaction from the vaccine.
In the two years since Gardasil came on the market, the government's Vaccine Adverse Event Report System database has received a few dozen reports of Guillain-Barré syndrome following Gardasil vaccination. This severely paralyzing (but reversible) condition was initially thought to be the cause of Jenny's and Whitney's paralysis until their symptoms continued to worsen. Tetlock wonders if others in the VAERS database might have also been misdiagnosed with GBS. Iskander tells me he doesn't think this is the case, and the rate of GBS in those vaccinated with Gardasil—about 1 to 2 per 100,000—is what you'd expect to see in the general population. But the VAERS database is based on voluntary reporting by doctors and patients, so underreporting is rampant and filings may lack crucial information. While it's fairly good at picking up common problems, experts say, it's likely to miss a small increased risk of rare conditions.
For now, the CDC has no worries over the safety of Gardasil. Iskander puts it this way: "While there is no such thing as a completely safe medical product, the available evidence suggests that benefits of this vaccine outweigh the risks." But concerning Jenny and Whitney, he does add, "we'll certainly be on the lookout if additional cases emerge." Says Shapiro: "I suspect if they get a third case, they'll have to really take notice, and they should."