Opposing concerns over increased promiscuity following HPV vaccination, a new large study published in CMAJ finds that the introduction of the routine HPV vaccination has not affected the sexual behavior of teenage girls.

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More than 40 HPVs can be easily spread through direct skin-to-skin contact during vaginal, anal and oral sex.

Human papillomavirus (HPV) is a common virus that is spread through sexual contact. Often, HPV is not symptomatic, and people are unaware that they have contracted the virus.

There are approximately 40 types of genital HPV. Some types can cause cervical cancer in women and can also cause other types of cancer in both men and women. Other strains can cause genital warts in both sexes. The HPV vaccine works by preventing the most common types of HPV that cause cervical cancer and genital warts. It is given as a three-dose vaccine.

In 2006, 49 countries licensed Gardasil, a quadrivalent HPV vaccine designed to protect against four types of HPV (6, 11, 16, 18) that cause 70% of cases of cervical cancer and most cases of anogenital warts. By 2012, the vaccine had been approved in almost 100 countries, many of which also implemented nationwide HPV vaccination programs aimed at immunizing young girls before the onset of sexual activity.

The large-scale immunization programs have been met with approval and controversy regarding the unanswered questions about the real-world effects of the vaccine.

A major topic of public debate has been the possibility that HPV vaccination might give women and girls a false sense of protection against all sexually transmitted infections and that this false sense of protection might lead them to engage in more risky sexual behaviors. Increases in risky behaviors, such as heightened promiscuity and neglecting condom use, could have important clinical consequences, including increased risk of pregnancy and sexually transmitted infections.

This population-based retrospective cohort study aimed to assess the effect of HPV vaccination on clinical indicators of sexual behavior among adolescent girls based in Ontario, Canada.

The researchers identified a population of 128,712 girls eligible for Ontario’s grade 8 HPV vaccination program in the first 2 years it was offered – 2007/2008 and 2008/2009. These eligible girls were compared with girls in grade 8 from 2 years before the vaccination program began, who were ineligible for publicly funded, school-based HPV vaccination – 2005/2006 and 2006/2007.

The cohort members were followed for an average of 4.5 years, and data was collected on indicators of sexual behavior such as pregnancy and non-HPV-related sexually transmitted infections in grades 10-12.

The results of the study highlighted 6% of cohort members with indicators of sexual behavior between September 1st of grade 10 and March 31st of grade 12:

  • 10,187 pregnancies
  • 6,259 with a non-HPV-related sexually transmitted infection.

Only 51% of eligible girls received all three doses of the HPV vaccine in grades 8 and 9. Girls born during the first quarter of each year, January-March, were consistently at a higher risk of outcomes than those born later in the year.

The authors observed no statistically significant increase in the risk of indicators of sexual behavior in relation to HPV vaccination.

Dr. Leah Smith, from the Department of Epidemiology, Biostatistics and Occupational Health at McGill University in Montréal, Canada, and Dr. Linda Lévesque, from the Department of Public Health Sciences at Queen’s University in Ontario, say the “findings suggest that fears of increased risky sexual behavior following HPV vaccination are unwarranted and should not be a barrier to vaccinating at a young age.” They continue:

Neither HPV vaccination nor program eligibility increased the risk of pregnancy and non-HPV-related sexually transmitted infections among females aged 14-17 years.”

Alleged to be the largest study on the association between HPV vaccination and proxies of sexual behavior, this study reports similar results to a US study on the topic involving 1,398 teenage girls.

“The results of this study can be used by physicians, public health providers and policy-makers to address public and parental concerns about HPV vaccination and promiscuity,” the authors conclude.

Medical News Today reported in July that vaccine coverage among US adolescents remains “unacceptably low.” It was estimated that in 2013, only 57% of girls and 35% of boys aged 13-17 years received one or more doses of the HPV vaccine.