How Long Will Gardasil’s 3-Shot Series Be Effective?

Update: As of May 8 2009, Merck reported that Gardasil showed a 96 percent protection against HPV type 16 after 8.5 years. That strain, one of four, covered by the vaccine, currently accounts for about 53.2 percent of invasive cervical cancers although a recent study showed that 16 was already losing ground to non-vaccine HPV types prior to the introduction of Gardasil.

At the same time, Merck reported that researchers had found a 17 to 45 percent reduction in abnormal Pap smears for vaccinated subjects in two randomized, placebo-controlled trials, 3.6 years into the study. The subjects had tested negative for HPV at the start of the study and had had normal Pap smears.


Proponents of Merck’s HPV vaccine, Gardasil, are quick to dismiss its side-effects as well worth the risk. After all, it’s the first vaccine against cancer, protecting young girls against perhaps 70 percent of the strains of HPV that can cause cervical cancer as well as some unpleasant little items like genital warts.

But how long will that protection actually last?

My daughter’s doctor couldn’t answer, even though he advised me to get her the shot. Merck’s own Gardasil website doesn’t address the question, nor does it provide a mechanism for asking it.

According to the National Cancer Institute’s website, Gardasil might only protect against HPV for four years. “The duration of immunity is not yet known. Research is being conducted to find out how long protection will last. Studies thus far have shown that Gardasil can provide protection against HPV 16 for 4 years.”

The Centers for Disease Control says in one area of its website only that “research suggests” that Gardasil’s protective effect should last for “a long time”, and in another that “studies have so far shown that vaccinated persons are protected for five years.”

And Gail Javitt, Deena Berkowitz, and Lawrence O. Gostin state in an article published in the Journal of Law, Medicine and Ethics that “One study indicates that protection against persistent HPV 16 infection remained at 94 percent 3.5 years after vaccination with HPV 16.34. A second study showed similar protection for types 16 and 18 after 4.5 years.”

Girls as young as nine are now receiving the series of three shots and it’s routinely recommended for girls of eleven and twelve. These girls will perhaps need to receive a booster shot in their mid- to late teens, and regularly after that. Cervical cancer has an incubation period of 7 to 20 years and is rare in women under 40; the average cervical cancer patient is 48 years old.

Women who had received the rubella shot as children of the sixties will remember being advised to have another shot prior to trying to conceive because the vaccine had not proved to be effective over the long haul.

At this point there doesn’t appear to be a clear plan for ensuring continued immunity, although research is ongoing and will doubtless address questions about the cumulative effect of necessary booster shots along with the original 3-shot series.

What do you think? Has enough research been done on length of time that Gardasil protects against HPV and the cumulative effect of booster shots? Would you be (or would you have been) willing to have the 3-shot series, or have your daughter take it, knowing that booster shots might be necessary? Please share your experiences!