"If they've only had one dose and they've had no problems with it, it could make sense to pull out and not do any more doses," said Dr. Diane Harper, director of the Gynecologic Cancer Prevention Research Group at University of Missouri. "If they've had two doses, they've already swallowed the fish hook. If nothing bad happened, after the third dose the chances of an [adverse event] are really, really small."
Harper added that parents, particularly those whose daughters are 11-12 years old, may want to carefully consider whether to continue administering Gardasil compared to girls who are receiving the vaccine in their late teens or early 20s, when the vaccine has a greater beneficial impact.
But others argue that vaccinating early provides protection before exposure to HPV and would not counsel the parents of a pre-teen differently than the parents of an older girl.
"At that [11-12] age group, they are getting lots of other shots, they're in the pediatrician's office," said Dr. Kevin Ault, associate professor of Gynecology and Obstetrics at Emory University. "If anything we want to aim younger rather than older."
The uncertainty of future consequences of the vaccine may be most troubling to parents who wish to protect their daughters from HPV and potential cervical cancer.
"I'm worried about the long-term effects of a vaccination [for which] they don't know the results," said Mimi Denhart, 45, whose 12-year-old daughter received her first dose of Gardasil last week.
Shapiro said that the long-term effects are not known and cannot be known until after future analysis but that any potential risk is a well calculated one.
"That effectiveness is going to be long term ... takes a certain leap of faith but it has been true of most vaccines," he said. "We can change and adapt as we get more information, but the best information [available] now is that the benefits exceed the risks."