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The quadrivalent human papillomavirus (HPV) vaccination is recommended for boys and girls starting at around the ages of 11 and 12. The vaccine protects against HPV strains that can cause cervical cancer. However, some research suggested that the vaccine could be tied to subsequent venous thromboembolism (VTE), also known as a blood clot. In a new study, researchers examined this risk in women and found that the vaccine was not tied to an increased risk of VTE.

"Safety concerns can compromise immunization programs to the detriment of public health, and timely evaluations of such concerns are essential," the authors wrote according to the press release. "Our results, which were consistent after adjustment for oral contraceptive use and in girls and young women as well as mid-adult women, do not provide support for an increased risk of VTE following quadrivalent HPV vaccination."

In this study, the research team headed by Nikolai Madrid Scheller, M.B., of Statens Serum Institut, Copenhagen, Denmark examined data taken from Denmark's national registers. The researchers focused specifically on the relationship between the HPV vaccine and risk of VTE. The team also had information on the women's vaccination history, oral contraceptive use, and use of blood thinners, also known as anticoagulants. The researchers examined the results of women who had a hospital diagnosis of VTE that was not tied to pregnancy, surgery, or cancer.

There were a total of 1,613,798 female participants between the ages of 10 and 44. 31 percent of them, or 500,345, were vaccinated from October 2006 through to July 2013. Overall, there were 4,375 cases of VTE with 20 percent of them, or 889, occurring in women who got vaccinated during the study period. Based on these cases, the team examined the individual's risk. They concluded that within the 42 days following a vaccination, the women did not have an increased risk of VTE.

The study was published in JAMA.