Some people have taken issue with the conclusion and analysis in my previous post, “Should Boys Be Given the HPV Vaccine? The Science Is Weaker Than the Marketing,” including epidemiologist Tara Smith in her blog, Aetiology, at ScienceBlogs. Here’s a clarification of some of the points in my post, and a response to some of hers.
First I’ll reiterate the key point of my post: There are many, many instances in which researchers have promised cures and interventions that were expected to work based on eminently reasonable logic, but did not pan out. Take one recent recent example: bypass a clogged artery and you will prevent strokes (see Sharon Begley’s excellent blog post on “When Biology Refuses to Listen to Medical Logic”). And now comes one more eminently logical assumption: prevent cervical lesions from some strains of HPV in some people for some period of time, and you will save lives from cervical cancer overall. Unfortunately, while the two HPV vaccines on the market may decrease the serious illness and death from cervical cancer, no study has proved that at this point, since no study has been conducted long enough to observe the development of cervical cancer or cervical cancer deaths.
Conclusive studies with the most important, clinically relevant end points should precede wide uptake of any intervention. The data currently rely on surrogate end points (markers of possible cancer) and are simply not conclusive. So we can’t truly say how effective the vaccine is.
Wake Forest medical researcher Curt Furberg, a former FDA advisor and co-author of the textbook Fundamentals of Clinical Trials, told me, “Getting data from markers is a first step. But we have burned our fingers too many times with surrogate markers. You should try to determine the real health benefit. Everything will be up in the air until we have the answer to the question: Will it prevent cancer? And until we have that answer, we should limit its use to girls enrolled in studies of the vaccine.”
Here are some other reasons why the HPV vaccines may not be as effective as advertised:
Merck’s promotion of Gardasil, its vaccine against the human papilloma virus (HPV), has a complicated history. First there was the exuberant claim about its reputedly great effectiveness in preventing cervical cancer. Now comes the recommendation last month from the Centers for Disease Control and Prevention, that all 11- and 12-year-old boys should be given the vaccine.
Of Science and Truthiness
The vaccine for boys is important, say advocates, because reducing HPV in boys will reduce transmission to girls and women—only 32 percent of whom have been getting the shots to date. Giving the shots to boys, they say, promotes gender equity. As a bonus, the vaccine may protect against oral and anal cancers in men who have sex with men.
Since a key part of the rationale for vaccinating boys is to protect girls, it’s worth a moment to examine the claims about reducing cervical cancer deaths. Merck won approval for Gardasil from the Food and Drug Administration in June 2006. On May 10, 2007, Merck published the results of a study in the New England Journal of Medicine that claimed an astounding 98 percent efficacy in preventing changes in the cervix used as a marker for cervical cancer.
But that statistic begs closer examination.