1. Relative to non-vaccinated girls, there was no increase in rates of sexually transmitted infections (STIs) following HPV vaccination.
Evidence Rating Level: 2 (Good)
Study Rundown: Nearly 25 percent of girls ages 14-19 and 45 percent of girls ages 20-24 are affected by human papillomavirus (HPV) each year. HPV is associated with genital warts and is the primary cause of cervical cancer. In 2006, the FDA approved the first quadrivalent HPV vaccine, covering the most common and most dangerous strains of the virus. The Advisory Committee on Immunization Practices (ACIP) recommends females ages 11-26 and males ages 11-21 be vaccinated. Despite this recommendation, HPV vaccination rates among US females remains low, with only 57 percent of adolescent females and 35 percent of males initiating the three-dose series. Many parents cite concerns that vaccination against HPV will promote unsafe sexual activity. In this study, researchers addressed that concern by looking at whether HPV vaccination in females was associated with an increased incidence of sexually transmitted infections (STIs).
In this study of over 200 000 adolescents ages 12-18, HPV vaccination was not associated with an increased rate of STIs. A strength of this study was the comparison of changes in STI rates before and after vaccination rather than just post-vaccination STI rates, which could have been biased by an increase in STI rates with increasing age. Limitations included the fact that insurance claims may miss STI diagnoses and HPV vaccinations that occurred at clinics that did not bill insurance. Additionally, they did not include uninsured patients or those with public insurance, a large segment of the population at risk. Future studies in a more diverse population would solidiy the findings presented herein.
In-Depth [retrospective cohort study]: Using a United States insurance database of females ages 12-18, researchers compared rates of STIs among girls who received the HPV vaccine (n=21 610) compared with those who did not (n=186 501). STIs that were included were chlamydia, gonorrhea, herpes, HIV/AIDS and syphilis. Changes in STI rates among HPV-vaccinated females before and after vaccination were compared to change in age-matched non-vaccinated females.
STI rates in the year before vaccination were significantly higher in HPV-vaccinated girls compared with non-vaccinated girls (4.3 vs. 2.8 per 1000, aOR=1.37, p=0.007). There was no difference between the two groups in age-associated increase in STIs one year after vaccination (aOR=1.05, p=0.74). This association held in subgroup analysis of 12-14 years olds, 15-17 year olds and those who use contraception.
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