We appreciate the interest of Dr Brewer in our study.1  We would like to clarify that our objective was not to assess the trends in HPV vaccine hesitancy in the United States overall. As we described, our motivation was to determine the proportion of parents who refused to initiate the HPV vaccine series “despite having received a provider recommendation.”

To simply explain our findings, let us assume that in 2012, of 1 million US adolescents, 460 000 (46%) were unvaccinated (received 0 doses), and of those adolescents, parents of 138 000 (30%) had received a provider recommendation. Among the parents who received a provider recommendation, 69 000 parents (50%) indicated, “they will not initiate the HPV vaccine series in the next 12 months” (ie, despite having received a provider recommendation). In 2018 (for the sake of simplicity, let us assume that the population size was constant), given the improvements in uptake, 300 000 (30%) adolescents were unvaccinated (ie, coverage improved). Of these, 150 000 (50%) had received a provider recommendation (percentage of parents of unvaccinated adolescents receiving recommendations also increased, as we documented in our study). Now, among 150 000 parents who received a recommendation, if we assume that similar to 2012, parents of ∼50% of adolescents were reluctant to initiate the series, the number of parents lacking intent will be 75 000. However, what we found was that the lack of intent in this subset was higher (64% [our outcome of interest]) in 2018 (ie, 96 000 parents responded that they would not initiate the series despite having received a provider recommendation). Note that parents who lack the intent to initiate the HPV vaccine series have increased from 69 000 to 96 000 despite increased coverage. (Although we assumed a constant denominator for this example, newer vaccine-eligible adolescents will get added to the cohort each year given the increasing population size.)

Let us walk through the actual numbers in the NIS database. In the 2012 survey, parents of 31 792 teenagers participated. Of the adolescents, 17 832 were unvaccinated and 2456 reported a lack of intent despite provider recommendation. In 2018, 38 706 participated, 12 798 were unvaccinated, and 3823 reported a lack of intent despite recommendation. The survey-weighted estimates of vaccine refusal despite having received a provider recommendation were 50.3% in 2012 and 63.9% in 2018. Although the NIS does not recommend calculation of the proportion by using the overall sample (individuals outside of the domain), if we divide the absolute numbers above, the proportions based on the overall samples (total respondents) will be 7.7% (in 2012) and 9.9% (in 2018), which is higher in 2018. (Note: The NIS collects responses on the parental intention to vaccinate only among unvaccinated adolescents; therefore, the NIS analytical guidelines recommend that the analysis should be performed within this subpopulation [ie, the domain (please see the NIS analytical guidelines for the “domain analysis”)]).2 

There is no perfect linear inverse relationship between receipt of recommendation and lack of intent. Providers should be applauded for the impressive improvement in recommendations. However, the rise in proportion of parents who are reluctant to initiate the HPV vaccine series despite having received a provider recommendation is a question worth exploring, and we hope answers will be provided in future studies.

, et al
HPV vaccine recommendations and parental intent
National Center for Immunization and Respiratory Diseases; Centers for Disease Control and Prevention; National Opinion Research Center at the University of Chicago
National Immunization Survey-Teen: A User’s Guide for the 2017 Public-Use Data File

Competing Interests

CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose.