• Even more evidence that the HPV vaccine doesn’t make girls act irresponsibly

    From JAMA Internal Medicine, “Incidence of Sexually Transmitted Infections After Human Papillomavirus Vaccination Among Adolescent Females“:

    IMPORTANCE Human papillomavirus (HPV) vaccination rates among US females remain low, in part because of concerns that HPV vaccination may promote unsafe sexual activity by lowering perceived risks of acquiring a sexually transmitted infection (STI).

    OBJECTIVE To study whether HPV vaccination of females is associated with increases in STI rates.

    DESIGN, SETTING, AND PARTICIPANTS Using a large, longitudinal insurance database of females aged 12 to 18 years insured from January 1, 2005, through December 31, 2010, in the United States, we examined whether HPV vaccination was associated with an increase in incident STIs among females who were vaccinated compared with those who were not. We defined STIs as one or more medical claims for any of the following infections in a given quarter: chlamydia, gonorrhea, herpes, human immunodeficiency virus or AIDS, or syphilis. We used difference-in-difference analysis to compare changes in STI rates among HPV-vaccinated females before and after vaccination (index quarter) to changes among age-matched nonvaccinated females before and after the index quarter. We analyzed whether effects varied according to age and prior contraceptive medication use.

    MAIN OUTCOMES AND MEASURES Rates of STIs

    I’ve discussed this before.

    There are people out there who refuse to let their girls get vaccinated against HPV because they’re convinced it’s a licence to have sex. Previous studies have refuted this. Here’s another. Researchers used pharmacy and medical claims data from 2005-2010 to look at whether HPV vaccination was associated with the likelihood of a girl having an sexually transmitted infection. To please Austin, they used a difference-in-difference analysis.

    In the year BEFORE vaccination. the rates of STIs were higher in those who would eventually vaccinate (4.3 per 1000) than those who would not (2.8 per 1000). In other words, there were differences there before vaccination occurred. Another way of looking at it is that girls who get vaccinated may be different than those who don’t. It’s correlation, not causation.

    Anyway, in the year after vaccination, STI rates went up in both groups – vaccinated (6.8 per 1000) and unvaccinated (4.2 per 1000). They got older, and they were likely more sexually active. But the difference-in-difference analysis showed that the increase in STIs was not related to the vaccine. Not among 12-14 year olds, not among 15-18 year olds, not among all of them together. It didn’t make a difference.

    Vaccinate your girls – and your boys – against HPV.

    @aaronecarroll

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