Using a large medical claims database, U.S. researchers compared rates of STI diagnoses (chlamydia, gonorrhea, herpes, HIV/AIDS, and syphilis) between vaccinated and unvaccinated girls aged 12 through 18 from 2005 through 2010. Over 20,000 girls who received the quadrivalent HPV vaccine were matched to 185,000 unvaccinated controls.
The STI rate increased in the year after vaccination among the vaccinated girls — but it also increased during the same period among the unvaccinated controls. After adjustment for more STIs before vaccination in the vaccinated group, the STI rate did not differ between the two groups.
Dr. Anna Wald of NEJM Journal Watch Women's Health commented: "These data add to the prior evidence that vaccination against HPV does not lead to increased sexual activity, but that sexual activity occurs as part of normal maturation among girls."
JAMA Internal Medicine
Background: NEJM Journal Watch Pediatrics and Adolescent Medicine summary of 2012 study showing no increase in STIs or pregnancies after HPV vaccination