Vaccine hesitancy is considered one of the 10 leading threats to global health, but there are little national data on the prevalence of parental hesitancy about childhood vaccines in the United States. Using an online panel, researchers surveyed a nationally representative sample of families with children ranging in age from six months to younger than 18 years. They sought to assess and compare the prevalence of hesitancy about routine childhood and influenza vaccinations, determine the relationship between hesitancy and deferral or refusal of vaccinations, and assess associations between sociodemographic characteristics and vaccine hesitancy.

Vaccine hesitancy was measured using a validated five-point scale, on which a score of more than 3 indicated hesitancy. Of the 4,445 parents sampled, 2,176 completed the survey, with 2,052 eligible respondents.

The prevalence of hesitancy regarding routine childhood vaccines was 6.1%; for the influenza vaccine, it was 25.8%. Concern about serious side effects was the factor most associated with childhood vaccine hesitancy: 12% of respondents strongly endorsed this concern, whereas 27% somewhat endorsed it. Concerns about safety were identical for both routine childhood and influenza vaccines. Whereas 70% of respondents strongly agreed that routine childhood vaccines are effective, only 26% felt the same about the influenza vaccine. Hesitancy rates were higher for respondents who held a degree less than a bachelor's and had a household income less than 400% of the federal poverty level.

Although the researchers used a validated scale to measure hesitancy, they acknowledge that survey data have inherent potential weaknesses, including reporting bias based on social desirability. Also, they point out that using different cutoffs to define hesitancy could have resulted in different results. In addition, the response rate in this study was only about 50%.