Worries about increased sexual activity are not the biggest issue for parents who opt not to have their children immunized against human papillomavirus (HPV), according to a new study.

The report in the Journal of Adolescent Health suggests that concern motivates only a small percentage of parents.

Instead, based on an analysis of survey data, Johns Hopkins researchers suggest that worries about safety, belief that the vaccine isn’t necessary, lack of knowledge about HPV, and absence of physician recommendations are much more important factors in parents’ hesitancy to have their children vaccinated.

Despite public-health recommendations to include the vaccine as part of the routine childhood series, current use remains relatively low in the United States. In 2016, the most recent year for which data on vaccination rates are available, only 50% of eligible females and 38% of eligible males had completed the vaccine series, the study points out.

“We wanted to better understand why parents choose not to vaccinate their children against HPV, since that information is critical for developing improved public health campaigns and provider messages to increase vaccination rates,” explains study coauthor Anne Rositch, MSPH, PhD.

The 2010–2016 National Immunization Survey-Teen (NIS-Teen), a series of annual vaccine-monitoring surveys conducted by the CDC, was used in the research. NIS-Teen collects information from a nationally representative sample of parents about their children’s vaccine usage, with vaccine rates verified using information collected from each child’s physician.

One open-ended question was whether parents planned to vaccinate their children against HPV if they hadn’t already, and, if not, why not. The first year the question was asked, 2010, responses were available from 3,068 parents of girls and 7,236 parents of boys aged 13 to 17 years. At the end of the study period (2016) 1,633 parents of girls and 2,255 parents of boys aged 13 to 17 years responded.

Results indicate that, for girls, safety concerns were the most common reasons in 2010 (23%) and 2016 (22%). Lack of necessity (21% vs. 20%), knowledge (14% vs. 13%), and recommendation (9% vs. 10%) remained stable, whereas child’s lack of sexual activity decreased from 19% to 10% (P <.01).

For males, lack of necessity (24% vs. 22%), recommendation (22% vs. 17%), and knowledge (16% vs. 14%), along with child’s lack of sexual activity (16% vs. 9%) and gender (13% vs. 2%), decreased from 2010 to 2016 (P <.05). Safety concerns, however, increased (5% vs. 14%) (P <.01).

“Vaccine messages should reflect current trends and focus on persistent concerns about knowledge, safety, and necessity, rather than sexuality and gender,” the study authors conclude.

Background information in the articles suggests that getting the HPV vaccine is important because it can protect against nine cancer-causing strains of HPV. The recommended dosing schedule for the vaccine now involves two injections if the first is administered before age 15 years, or three injections if the first is administered after age 15 years.

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