Introduction: In 2018, the U.S. Food and Drug Administration extended the licensure for human papillomavirus vaccination to include everyone aged 27–45 years. In 2019, the Advisory Committee on Immunization Practices issued a recommendation that adults aged 27–45 years and their providers engage in shared clinical decision making about human papillomavirus vaccination. In addition, in 2019, the Advisory Committee on Immunization Practices reiterated that all previously unvaccinated individuals receive catch-up vaccination through age 26 years. This study estimates the pre-recommendation prevalence of human papillomavirus vaccination and factors associated with vaccination in 2 age groups (19–26 years [young adults] and 27–45 years [mid-adults]), forming a baseline to monitor future coverage among U.S. adults. Methods: The final sample included 9,744 individuals (2,522 young adults and 7,222 mid-adults) who participated in the 2017 National Health Interview Survey. The main outcomes were receipt of 1 or more human papillomavirus vaccination and whether the participant had been vaccinated as an adult. Demographic characteristics and healthcare factors were included as covariates in statistical analyses. Results: Population estimate of receiving 1 or more human papillomavirus vaccine doses among young adults was 36.3% (female: 51.5%, male: 21.2%; p<0.001) and 9.7% for mid-adults (females: 15.8%, males: 3.2%; p<0.001). In the best-fit model, age was inversely associated with vaccination for mid-adults (female: OR=0.84, 95% CI=0.81, 0.86; male: OR=0.86; 95% CI=0.82, 0.90) and male young adults (OR=0.79, 95% CI=0.71, 0.88). Of the entire vaccinated sample aged 19–45 years, 26.6% had received their first vaccination as an adult (95% CI=23.9, 29.4). Conclusions: These data emphasize the continued need for vaccinating adolescents aged 11–12 years given that few adults were vaccinated against human papillomavirus.