HPV Vaccine in Teens: No License for Sexual Activity
William T. Basco, Jr., MD, MS
March 11, 2015
Incidence of Sexually Transmitted Infections After Human Papillomavirus Vaccination Among Adolescent Females
Jena AB, Goldman DP, Seabury SA
JAMA Intern Med. 2015 Feb 9. [Epub ahead of print]
Study Summary
Despite the fact that 45% of women aged 20-24 years have evidence of exposure to human papillomavirus (HPV), uptake of the HPV vaccines has significantly lagged behind that of other adolescent vaccinations. The three-dose nature of the vaccine contributes to the difficulty in completing the series, but persistent concerns that vaccination might lead to sexual promiscuity continue to be raised in studies that evaluate barriers to delivery. Although smaller previous studies have demonstrated a lack of association between HPV vaccination and later promiscuity or measures of high-risk sexual behavior, this study used longitudinal data from large, nationally representative insurance samples to address the question. The data were collected from the period January 1, 2005 through December 31, 2010, from 41 employer-provided health plans. Girls aged 12-18 years who had received at least one dose of the HPV vaccine were identified and matched with at least one unvaccinated adolescent in the same age range, residing in the same zip code, and enrolled in the same health plan.
The primary outcome was whether the teen had any sexually transmitted infection (STI) from among the following: chlamydia, gonorrhea, herpes, HIV, or syphilis. To account for selection bias in who decides to receive the HPV vaccine as well as for temporal trends, girls were stratified according to STI frequency in the year "before" and the year "after" the vaccine series was given. A "difference-in-differences" was calculated to detect any increase in STI frequency in the vaccination group compared with the temporal trends observed in the unvaccinated group. The analysis controlled for whether the adolescents were taking contraceptive medications before vaccination as an additional method to control for prevaccine sexual activity and selection biases introduced by who chooses to become vaccinated.
Study Findings
In the first year of data, only 2.5% of girls had received the vaccine, compared with 27.3% by the end of 2010. More than 21,000 girls were vaccinated against HPV in the dataset, and they were matched to more than 186,000 unvaccinated girls. Those who received vaccine were more likely to have had at least one STI in the year before vaccination (4.3 STIs per 1000 vaccinated girls vs 2.8 per 1000 matched unvaccinated girls).There was also a higher frequency of having received contraception in the year before vaccination in the vaccinated girls compared with their matched controls. In the year after vaccination, both the vaccinated and unvaccinated girls experienced higher frequencies of STI. Furthermore, the frequency of STI was always higher in the group who received vaccination. However, the ratio of the difference between the two groups was not significant. The difference-in-differences odds ratio was 1.05 (95% confidence interval, 0.80-1.38), suggesting that the there was no difference in the relative increase in STIs between the vaccinated and unvaccinated groups. A similar pattern was found when the groups were subdivided by age (12-14 years and 15-18 years).
The investigators concluded that HPV vaccination was not associated with increases in STI in this very large sample of adolescent girls. They suggest that vaccination with HPV is not likely to lead to risky sexual behavior.
Viewpoint
In reality, this study supports what several previous smaller studies have found: Administering the HPV vaccine to adolescent girls does not offer a license for sexual activity. It is helpful for pediatric clinicians to have these data in mind when having discussions with parents. However, one of the most effective ways to improve HPV vaccine is to not treat HPV vaccine differently from any other adolescent vaccinations. Certainly, school mandates would help, but in the meantime, approaching this vaccine as if it were "no big deal" in pediatric offices would improve its acceptance and increase rates of delivery.
