The safety of vaccines used to prevent human papillomavirus (HPV), one of the most common sexually transmitted infections and the cause of various cancers, has been thoroughly assessed in women but not men, a new study asserts.

The report in the British Journal of Clinical Pharmacology points out that three HPV vaccines are now available. A new analysis led by Italian researchers from the University of Bologna sought to determine if HPV vaccines are safe and well tolerated in the male population and if side effects that may occur after immunization are similar in both sexes.

For the analysis, the researchers reviewed all reports of adverse events following immunization present in the U.S. Vaccine Adverse Event Reporting System from “January 1, 2006 to September 30, 2018.

"To the best of our knowledge, this is one of the first studies focused on the evaluation of the safety profile of HPV vaccines in males," the authors write.

The pharmacovigilance study notes that HPV is linked to several different types of cancer—cervical, penile, vulvar, anal, and oropharyngeal—and can affect both males and females. Researchers say they sought “to enrich the knowledge on the safety profiles of HPV vaccines in the male population.”

Based on 5,493 reports retrieved, the study found that the most report events—and that proportionally occurred more frequently with HPV vaccines than with others in males—were syncope (n = 701, reporting odds ratio [OR] = 2.85 [95% CI = 1.41–5.76]), loss of consciousness (n = 425, OR = 2.79 [CI = 1.36–5.72]), and fall (n = 272, OR = 3.54 [CI = 2.00–6.26]).
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The majority of "the adverse events following immunizations were already reported in premarketing clinical trials and acknowledged for the corresponding vaccines,” the authors conclude. “A disproportionate reporting was found for some of these events including syncope. The HPV vaccines are generally well tolerated in males, although limitations own of spontaneous reporting should be considered.”

The CDC recommends HPV vaccine for routine vaccination at age 11 or 12 years, although vaccination can be started at age 9 years. The CDC’s Advisory Committee on Immunization Practice also recommends vaccination for everyone through age 26 years if not adequately vaccinated previously. HPV vaccination is given as a series of either two or three doses, depending on age at initial vaccination, and can be given to older adults in certain circumstances.
 
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