Study: HPV vaccine, riskier sexual activity not linked

The sexual behavior of teenage girls does not appear to be affected after they obtain the human papillomavirus (HPV) vaccine, according to a new study in the Canadian Medical Association Journal (December 8, 2014).

Some physicians and dentists have been reluctant to recommend the vaccine, because it may be seen by parents as encouraging and/or condoning sex among adolescents. There have been concerns that the vaccine, which guards against four types of the HPV shown to cause cervical cancer and anogenital warts, may give girls a false sense of security about contracting sexually transmitted infections (STIs) and lead them to engage in riskier sexual activity, the study authors noted.

Leah Smith (left) and Linda Lévesque, PhD, discuss the research findings. Image courtesy of Queen's University.

"These findings suggest fears of increased risky sexual behavior following HPV vaccination are unwarranted and should not be a barrier to vaccinating at a young age," said lead study author Leah Smith, a doctoral candidate at Queen's University in Kingston, Ontario, in a statement.

This research looked at a cohort of more than 260,000 girls, about half (almost 129,000) of whom were eligible for Ontario's publicly funded, school-based HPV vaccination program during the first two school years (2007-2008 and 2008-2009) it was offered. The girls were followed until March 31 of their grade 12 year. About 6% of the girls became pregnant or contracted an STI between grades 10 and 12, with 10,187 pregnancies and 6,259 STI cases not related to HPV.

"Neither HPV vaccination nor program eligibility increased the risk of pregnancy nor non-HPV-related STIs among females aged 14 to 17 years," said senior study author Linda Lévesque, PhD. "The results of this study can be used by physicians, public-health providers, and policymakers to address public and parental concerns about HPV vaccination and promiscuity."

Some of the more than 100 countries the vaccine is licensed in have reported HPV vaccinations rates greater than 90%, including many that distribute the vaccine in school-based programs, according to the study.

U.S. legislation that requires or encourages young people to get the HPV vaccine has been unsuccessful in getting more of them vaccinated, according to new research presented at the recent American Public Health Association meeting.

Currently, 23 U.S. states and the District of Columbia have laws that require HPV vaccinations, provide funding to cover the costs of the vaccines, or support public education about HPV and the vaccine. Only the District of Columbia and Virginia require the vaccine for girls to enter the sixth grade and, even there, parents can opt out.

The Centers for Disease Control and Prevention (CDC) recommends that all 11- or 12-year-old girls receive the vaccine in three doses. The CDC further recommends that all young women between the ages of 13 through 26 should get the vaccine if they have not received any or all doses when they were younger. For boys and young men, the CDC recommends the HPV vaccine for all boys age 11 or 12 years and also for males ages 13 through 21 who did not get any or all of the three recommended doses when they were younger. All men may receive the vaccine up to age 26.

Currently available HPV vaccines could prevent most oropharyngeal cancers in the U.S., according to a 2014 CDC study (Emerging Infectious Diseases, May 2014, Vol. 20:5, pp. 822-828).

In the U.S., the federally financed Vaccines for Children Program pays for vaccines recommended by the U.S. Advisory Committee on Immunization Practices (ACIP) for children ages 18 and younger who are either Medicaid-eligible, uninsured, American Indian or Alaska Native, or underinsured.

HPV has been causally linked to multiple cancers, including cervical and oropharyngeal cancers. The CDC reports that about 26,000 Americans are affected by HPV-related cancers annually. HPV is a sexually transmitted infection affecting between 0.9% to 7.5% of U.S. adults, according to a policy brief by the Center for Oral Health. Studies show the prevalence of genital HPV ranges from 27% to 43% among U.S. females ages 14 to 59 years.

The COH report recommends the HPV vaccine for all children between the ages of 10 and 14, because studies have shown the vaccine is most effective before the start of sexual activity, and the vaccine does not clear infections acquired before vaccination.

Vaccinations against HPV strains 16 and 18 currently available include Cervarix (GlaxoSmithKline) and Gardasil (Merck Sharp & Dohme).

A free, federal nationwide HPV vaccination program for adolescent boys and girls would save billions of dollars in medical costs and help prevent oropharyngeal cancers, according to the Center for Oral Health. Studies show that noncervical HPV-related diseases cost billions of dollars annually.