The HPV vaccination rate lags behind that of other vaccines, and a new study suggests that doctors may be a key part of the problem.

The study found that doctors don’t strongly recommend the vaccine, don’t discuss it in a timely manner, and tend to suggest it for young people they perceive to be at risk, rather than for all girls and boys. This study is a reminder of the confusion and controversy that has surrounded the HPV vaccine since it was approved for use almost a decade ago and suggests that these pervasive misunderstandings extend to the very people who should be promoting it the most.

The HPV vaccine protects against certain strains of the human papillomavirus, which can be sexually transmitted. The CDC estimates that 79 million people in the United States are infected with the HPV virus and 14 million new infections occur annually. Though most people won’t suffer long-term health consequences and may never know they have the virus, others may develop cervical cancer or cancers of the head, neck, throat, penis, or anus.

About 12,000 women in the United States develop cervical cancer each year and 4,000 women die from the disease.

The newest version of the HPV vaccine protects against nine strains of the virus, some of which are known to cause most cases of cervical cancer. Researchers have suggested that if this vaccine were to be widely used, it has the potential to prevent 90 percent of all cervical, vulvar, vaginal, and anal cancer.

Despite this potential to save lives, HPV vaccination rates have been lower than that for other recommended vaccines. In 2014, 60 percent of girls ages 13-to-17 received at least one of the three recommended doses of the HPV vaccine, but only 39.7 percent had received all three, as Rewire reported.

Rates of the vaccination for boys are lower, with 41.7 percent of boys age 13-to-17 having received at least one dose of the vaccine and 21.6 percent receiving all three. In contrast, 79.3 percent of teens age 13-to-17 had received the quadrivalent meningococcal conjugate vaccines (which protects against meningitis), and 87.6 percent had received the Tdap vaccine (which covers tetanus, diphtheria, and pertussis).

The new study suggests that doctors may contribute to this imbalance because they are not strongly promoting HPV vaccination for their patients. For the study, which was published in Cancer Epidemiology, Biomarkers & Prevention, researchers surveyed 776 physicians and asked about five communications practices that national guidelines suggest are necessary for delivering the vaccine. The practices include timeliness (did they recommend the vaccine by ages 11 or 12 or wait until patients were older, and did they recommend it for both boys and girls and boys?); consistency (did they recommend the vaccine for all patients or just those whom they considered at risk?); urgency (did they recommend getting it at the current visit or suggest parents go home and think about it?); and strength of endorsement (did they describe the vaccine is “very” or “extremely” important or were they less emphatic?).

They found that 26 percent of physicians said they don’t provide timely recommendations for girls and 39 percent said they don’t do timely recommendations for boys. Consistency was also low, as 59 percent of physicians acknowledged that they recommended the vaccine more for patients they perceived at high risk rather than recommending it for all of their patients.

Physicians were about equally split on the concept of urgency (51 percent recommend same-day vaccinations). Twenty-seven percent of physicians across the country admitted that they do not strongly endorse HPV vaccination.

The researchers were discouraged by their findings. “We were surprised that physicians so often reported recommending HPV vaccination inconsistently, behind schedule, or without urgency,” Melissa Gilkey, one of the study’s authors, said in a press release. “We are currently missing many opportunities to protect today’s young people from future HPV-related cancers.”

These missed opportunities come alongside growing evidence that HPV vaccines are reliably effective. A 2013 report by the CDC, for example, looked at some of the strains targeted by the vaccine. It compared the infection rate in girls 14-to-19 before the vaccine was approved and another from after it received government approval. The proportion of girls infected with the strains dropped by 56 percent.

This applies to all teens, whether or not they were vaccinated, and may be a result of what public health experts refer to as “herd immunity”—if enough of the population is protected by a vaccine, that protection extends to the unvaccinated as well. Among girls who had gotten the vaccine, however, the drop in HPV infections was even higher, at 88 percent.

Another study found that cervical cancer rates were lower in states that had higher rates of HPV vaccination. For example, 66 percent of young women in Vermont have received at least one dose of the vaccine and 5.4 women out of 100,000 are diagnosed each year. In contrast, 41 percent of girls in Arkansas have received one dose of the vaccine and 10.2 out of 100,000 women are diagnosed with cervical cancer each year.

Forty percent of girls in Mississippi received one dose of the vaccine and the cervical cancer rate is 9.2 per 100,000 women.

Doctors may be the key to boosting these vaccination rates. The study’s authors wrote that prior research has shown that a health-care provider’s recommendation is the single biggest influence on whether parents decide to get the HPV vaccine for their daughter or son.

Gilkey said there are easy changes providers can make. “Physicians have a lot of influence on whether adolescents receive the HPV vaccine. Our findings suggest that physicians can improve their recommendations in three ways: by recommending HPV vaccination for all 11- to 12-year-olds and not just those who appear to be at risk; by saying the HPV vaccine is very important; and by suggesting vaccination on the day of the visit rather than at a later date.”