The modelling has been done (The New England Journal of Medicine, vol 359, p 821) and suggests that vaccinating 12-year-old girls is worth it. However, the model includes a number of highly optimistic assumptions. Among these are that the vaccine offers lifelong protection with no need for a booster, that it has the same effect on young girls as older women, that HPV-16 and HPV-18 are not replaced by other cancer-causing strains, that vaccinated women continue getting screened for cervical cancer, and that natural immunity against HPV is unaffected.
Are these assumptions reasonable? We do not know. What we do know is that if they are not, vaccination is less effective and may even be less effective than screening alone. And what if the vaccine has long-term side effects?
With so many essential questions unanswered, there is good reason to be cautious about introducing large-scale HPV vaccination. Instead, we should concentrate on getting answers.
One thing's for sure though. Those answers are unlikely to emerge from the likes of Michele Bachmann.
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