Aug. 19, 2009 -- On Tuesday, ABC News' Chief Medical Editor Dr. Timothy Johnson wrote a blog entry that appeared on the World Newser about a new report in the Journal of the American Medical Association on the benefits and risks of Gardasil, the Merck vaccine against the human papilloma virus (HPV).
While side effects from the vaccine appear to be rare, the shot has been associated with effects ranging from fainting and nausea to life-threatening blood clots and other more severe complications.
In his entry, Johnson noted that he could not recommend that all girls and young women in the eligible age range for the shot get vaccinated based on what researchers currently know about the vaccine's risk profile.
The entry garnered a strong response from our audiences, as evidenced by the many questions that appeared on the comment boards following his post. Below, Johnson and other medical experts address some of the most commonly asked questions in response to the comments on the World Newser blog:
1) What should parents do if they have already had their daughters vaccinated?
For now, Johnson said, there is little that parents should be doing if their daughters have already received the HPV vaccine.
"They can't do anything about it now, and they should pay attention to any side effects symptoms that might show up," Johnson said, adding that there is no research yet that has suggested a point in time after which side effects will not arise. "Fortunately, the numbers in terms of incidence of these side effects appear very low, so parents should not worry unless something happens."
Dr. Eugene Shapiro, associate chair of the department of pediatrics at the Yale University School of Medicine, said that, though long-term data is not available, he believes that if a recipient of the vaccine has not had adverse reactions so far, there is a slim chance that they will.
"In my opinion, the benefits will far exceed any potential risks," Shapiro said.
2) The vaccine is given in three shots. If a girl has already had the first dose, should she take the remaining two doses in light of concerns over the HPV vaccine?
Physicians agreed that just because a girl has had the first shot of the HPV vaccine does not mean that she must necessarily complete the entire three-dose course.
"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 the University of Missouri.
Johnson agreed. "There is no easy answer to that question, because it really boils down to the question of whether they should have the shot at all," he said. "But the fact that they have had one dose, in my mind, shouldn't change the question. If they don't want it, then they should stop at one."
3) My 12-year-old daughter has already received two of the three doses. Should I allow doctors to give the third, and if not, are there any risks to only having two?
As with girls who have already received a single shot of Gardasil, those who have received two doses will not experience any additional risk if they opt not to have the third shot in the course, doctors said. But Harper noted that those girls who have had two doses of the vaccine already have very little to fear from a third dose if they, their parents and their doctor agree that it is the proper course of action.
"If they've had two doses, they've already swallowed the fish hook," she said. "If nothing bad happened, after the third dose the chances of an [adverse event] are really, really small."
Still, she said, parents, their daughters, and their doctors should probably weigh in the known benefits of the vaccine against the risks of opting for the third dose in the course.
"If they do not receive the three doses, the vaccine does not work at all," she said. "If they stop now, they have no benefit from what they have already done. If they continue, there is still a small probably very small but real chance of something happening after the upcoming dose."
For this reason, Shapiro said, those who have already started the course will probably be encouraged by their doctors to continue.
"We continue to counsel anyone who has already started the vaccine to continue the vaccine, especially if they've had no adverse reactions," Shapiro said.
4) Why are girls the only target of the vaccine?
"They're the ones who get cervical cancer, so they are the ones that we think about in terms of prevention," Johnson said. But he added that because the infection is carried and spread by boys as well, there is a rationale for prevention efforts in boys, too.
But, he added, the recent debate over the vaccine's effectiveness versus its possible risks could affect the debate on this issue as well.
"I doubt they will be going ahead with boys anytime soon," he said.
5) My daughter heard the news about Gardisil; now she is terrified. How, as parents, can we address her concerns?
Johnson said that the best move for parents is to allow their child to become part of the discussion that the family has amongst themselves and with the family doctor. And he said that even the youngest girls who may have received Gardasil shots are probably old enough to understand the issues at play in the editorial which accompanied the report in JAMA.
"Most 11- and 12-year-olds could read it and understand it, I feel," Johnson said. "They should be made part of the family discussion when it comes to reading this editorial and discussing the issue with the family doctor."
Most importantly, Johnson said, parents should take their daughters' concerns seriously.
"The worst thing to do is to shut them out of the discussion and tell them not to worry," he said.
Radha Chitale contributed to this report.