An interesting new study finds that parents who resist the HPV vaccine can be convinced to sign on to kids getting it — as long as they have the power to opt out. The HPV (human papillomavirus) vaccine remains a controversial subject due to the broader anti-vaccination movement, and just one in five parents support making the HPV vaccine — which was invented to prevent cancer — a requirement for school.

But this new study found out something interesting: parents would be a bit more comfortable with it if it wasn’t mandatory, according to a UNC Lineberger Comprehensive Cancer Center statement. And it wasn’t by a little bit either: having an opt out provision tripled the support of the vaccine.

Of course, that comes with a steep price: allowing people to opt out makes the vaccine a lot less effective. It puts health officials in a bit of a bind deciding whether it’s better to get broader support and a less effective law, or fight for a more effective law.

The HPV vaccine is recommended by the Centers for Disease Control and Prevention for girls and boys at the ages of 11 and 12. It has been determined to be effective at combating cervical cancer and has one of the strongest safety records of any vaccine.

“School entry requirements are highly acceptable to parents, but only when implemented in a way that makes them ineffective,” said the study’s senior author Noel Brewer, PhD, a member of the University of North Carolina Lineberger Comprehensive Cancer Center and an associate professor in the UNC Gillings School of Global Public Health. “Opt-outs lead to a large number of parents choosing not to vaccinate their children, and that makes requirements ineffective in raising vaccination rates.”