In 2009 and 2010, fewer than half of all US states reported that the proportion of children aged five to six who were properly vaccinated against measles before they entered school had reached the desired 95%. In parts of the country, the rate of refusal of mandatory childhood vaccinations for non-medical reasons stands at 25%. And as-yet-unpublished data show that this rate in continuing to increase.

The results of vaccine refusal are already evident in Europe. France reported 4,937 cases of measles in the first three months of this year — nearly as many as in all of 2010. In total, 30 countries in the World Health Organization's European region reported a marked increase in measles cases early this year. At some point, the herd immunity that protects the unvaccinated and the immunosuppressed could be lost.

Against this backdrop, it is vital that public debates on vaccination stick to the facts — and that politicians who make science-supported decisions be applauded. Unfortunately, it was Michele Bachmann who received the applause at the Republican presidential candidates' debate earlier this month. The Minnesota congresswoman had attacked rival candidate Rick Perry for his failed attempt in 2007, as Texas governor, to mandate vaccination against human papilloma virus (HPV) for 11- and 12-year-old schoolgirls, as recommended by the US Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia.

Perhaps Perry did the right thing for the wrong reasons: he has close ties to pharmaceutical company Merck, a generous donor to his campaigns and the only maker of an HPV vaccine at the time of his attempt. But his goal was laudable: HPV is the most common sexually transmitted infection in the country and the major cause of cervical cancer, which kills 4,000 US women each year. The Food and Drug Administration has also approved the HPV jab for the prevention of vulvar and vaginal cancers, and of anal cancer in both males and females.

That did not stop Bachmann from making the astonishingly irresponsible claim, on national television, that the vaccine is a “potentially dangerous drug”. She later suggested that it is linked to “mental retardation”. Yet the CDC says that the vaccine is safe. Some 35 million doses have been delivered in the United States since its approval, but just 0.05% of recipients have reported side effects, mostly minor. Nor is there scientific support for the belief that presumably drives Bachmann's misstatements — that vaccinating prepubescent girls will somehow encourage them to become sexually active.

If Bachmann wants to do right by the millions of girls she claims to care about, she ought to retract her words and urge HPV vaccination. That might do more than anything else to combat an increasingly common parental mindset that takes for granted the past century of gains against infectious disease, and in so doing threatens to reverse them.