Background: In the US, the HPV vaccine has been recommended for cancer prevention for girls since 2006 and boys since 2011; uptake has been consistently lower among boys. We evaluated if the established effect of parent/guardian HPV vaccine misperceptions on child HPV vaccination differed by child sex.

Methods: We conducted a cancer-focused population health assessment in San Diego County in 2019. Data were weighted to the county adult population. Prevalence ratios (PRs) and 95% confidence intervals (CIs) for the association between parent HPV vaccine misperceptions, assessed using the HPV Vaccine Misperceptions Scale (per standard deviation [SD]; higher scores indicate greater misperceptions), and their child not receiving the HPV vaccine were modeled using survey-weighted modified Poisson regression by child sex. Effect measure modification (EMM) was assessed using relative excess risk due to interaction (additive scale) and ratio of PRs (multiplicative scale) from a single model with joint indicators for child sex and HPV vaccine misperception scores.

Results: Our study sample (n=239) represented a weighted sample of 893,364 parents with HPV vaccine age-eligible children. Median parental scores (range: 0-36) were 11.0 (IQR=5-16) for parents of boys and 13.0 (IQR=8-19) for parents of girls; 64.3% of boys and 56.1% of girls were ever vaccinated. After adjustment, a one SD increase in parental misperception score was associated with a 75% prevalence increase of not vaccinating daughters (PR=1.75; 95% CI: 1.41, 2.10) and a 51% prevalence increase of not vaccinating sons (PR=1.51; 95% CI: 1.05, 1.97; Figure 1); however, EMM by child sex was not statistically significant (Ps≥0.05).

Conclusions: Higher parental HPV vaccine misperceptions were associated with not vaccinating both daughters and sons, with a stronger, but not significantly different association for daughters. Misperceptions measured by our scale do not appear to impact parents differentially based on child sex.