A new vaccine that broadens coverage against the human papillomavirus shows such potent protection for girls and women in a trial that some are calling the findings a milestone. Based on these results, reported in the Feb. 19 New England Journal of Medicine, the U.S. Food and Drug Administration has cleared this vaccine for use in girls and boys starting at age 9.
The added protection shown in this trial “is actually quite stunning,” says Margaret Stanley, an immunologist at the University of Cambridge. “These girls will be protected against 90 percent of cervical cancers and probably 80 percent of precancers” caused by HPV, she says, alluding to abnormal cell growth detectable by Pap smears.
There are dozens of types of HPV, and some cause cancer. Current vaccines guard against the two main carcinogenic HPV types, which trigger about 70 percent of cervical cancer cases. The new shot, dubbed Gardasil 9, adds components against five more carcinogenic types. It and a current Gardasil vaccine also protect against two HPV types that cause genital warts.
In the trial of more than 14,000 girls and women ages 16 to 26, half were randomly assigned to get three doses of Gardasil 9 over six months; the others got the original Gardasil. Participants were followed for up to 54 months. The new vaccine delivered more than 96 percent protection against the five added HPV types, says study coauthor Elmar Joura, a gynecologic oncologist at Medical University of Vienna.
In the Gardasil 9 group, only one person developed cervical cancer or abnormal cell growth caused by any of the five HPV types addressed by the vaccine, compared with 27 women who got the older Gardasil vaccine. Similarly, 35 volunteers receiving Gardasil 9 developed an HPV infection that lasted at least six months and was traceable to one of the five newly covered HPV types, compared with 810 of those who got original Gardasil.
HPV vaccines engender better immunity than an actual infection with HPV does, says Stanley, who wasn’t involved in the new study. That’s because an HPV viral infection is only skin-deep. “It never shows itself to the blood,” she says, “so you make a really wimpy immune response.” In contrast, the vaccines “go straight into the muscle and make a terrific response.”
The U.S. Centers for Disease Control and Prevention currently recommends that girls and boys get a three-shot HPV regimen at age 11 or 12. The CDC has yet to set recommendations specifically for the new vaccine. Since HPV is spread by sexual contact, full protection is most likely to occur if a child is immunized before becoming sexually active (SN: 4/20/13, p. 20).
The study is “a milestone in expanding the coverage of cancers associated with HPV,” physician Anne Schuchat of the CDC writes in the same issue of the New England Journal of Medicine. But as of 2013, only 57 percent of U.S. girls ages 13 to 17 had gotten even a single dose of the HPV vaccine. For boys that age, it’s only about 35 percent. “Vaccination of a much higher proportion of preteens is needed,” she writes. “Otherwise, decades from now oncologists will still be talking about HPV-associated cancers with thousands of new patients every year.” CDC reports that in 2011, 12,109 women in the United States were diagnosed with cervical cancer.
“The new vaccine, from my point of view, is wholly a good thing,” says clinical psychologist Gregory Zimet of Indiana University School of Medicine in Indianapolis — even for children or young adults who have already undergone a full or partial regimen of HPV shots. Getting a round of the broader-coverage new vaccine would be safe and would increase protection, he says.