Vaccines for human papillomavirus (HPV), given to girls to prevent cervical cancer, have come under fire in several countries for allegedly causing such side effects as difficulty walking, headache, fatigue, poor concentration, and pain. Numerous studies have found no causal link between the vaccine and these symptoms. But concerns have caused vaccination rates to collapse in Japan and to sag in other countries. Vaccine advocates warn this trend exposes women—and men—to preventable cancers and other illnesses. The debate is heating up over a recent paper that claims to show that the HPV vaccine affects the central nervous system in mice. Critics are attacking the paper’s methodology and conclusions and are asking the journal to retract it in light of the potential negative impact it could have on public health.