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Despite no observed changes in serious adverse event reporting trends for the human papillomavirus (HPV) vaccine, more parents are mentioning safety concerns when deciding against vaccinating their kids, a cross-sectional study found.

From 2015 to 2018, the proportion of parents who cited safety concerns as their primary reason not to initiate the HPV vaccine grew from 13% to 23% (P<0.001), representing a 79.9% increase, reported researchers led by Kalyani Sonawane, PhD, of the University of Texas Health Science Center School of Public Health in Houston.

Overall, 30 states saw this type of increase in parental hesitancy to the HPV vaccine, according to the findings in .

Yet over that time, adverse events reported to the Vaccine Adverse Event Reporting System (VAERS) decreased from 44 to 29 per every 100,000 doses distributed (P<0.001). And there were no changes in serious reporting rates for events that led to either hospitalization or disability, a life-threatening condition, or death.

"These findings suggest an urgent need to combat the rising sentiment of safety concerns among caregivers to increase HPV vaccine confidence," wrote Sonawane and colleagues.

HPV vaccination can prevent six types of cancer (vulvar, vaginal, cervical, penile, oropharyngeal, anal), the researchers noted, and the study is the first to present nationwide trends evaluating adverse events reporting.

In an , Nosayaba Osazuwa-Peters, BDS, PhD, MPH, of Duke University School of Medicine in Durham, North Carolina, and colleagues, said the study "is a reminder that there may be more innuendos, half-truths, exaggerated case studies, and propaganda driving concerns about HPV vaccine safety than actual scientific facts."

"To be clear, social media is not to blame for all concerns about vaccine safety," they added. "There has always been resistance to vaccines, dating back to the polio vaccine and even before that."

For their study, Sonawane and colleagues conducted an analysis of VAERS and the National Immunization Survey (), including data from 2015 to 2018. NIS, performed by the CDC, consisted of a phone survey of adult caregivers' reasons for HPV vaccine refusal, and included reports on 39,364 unvaccinated adolescents.

The VAERS database was searched for adverse events associated with the Gardasil (approved in 2006) and Gardasil 9 HPV vaccines. Regulatory definitions defined serious and non-serious (95.6% of overall reports) adverse events.

Teenagers of NIS participants had an average age of 15 (range 13 to 17), over 60% were white, and over half male. Nearly 80% of participants lived above the poverty line and over 60% had private insurance.

States seeing the greatest increases in parental vaccine hesitancy due to safety concerns included South Dakota (7.8% in 2015 vs 26.6% in 2018), California (3.5% vs 20.5%, respectively), Mississippi (8.1% vs 24.4%), and Hawaii (5.8% vs 20.9%).

Outside of safety concerns, the other top reasons for HPV vaccine hesitancy, as reported by 75% of caregivers, included being "not necessary," "not recommended," not having sexually active adolescents, and lacking knowledge on them. All of these reasons showed decreasing trends over the study period.

The analysis had several limitations, the researchers acknowledged, including that the findings are not generalizable to other age groups. VAERS, a spontaneous reporting system, often lacks subsequently relevant accompanying data, and is therefore subjected to bias, they added.

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