Lack of knowledge about the human papillomavirus vaccine among Brazilian adolescents: A cross-sectional study.

To analyze the distribution and factors associated with lack of knowledge about the human papillomavirus (HPV) vaccine among Brazilian adolescents.Cross-sectional study using the 2019 National School Health Survey among 17,805 Brazilian students of public and private schools, aged 13-17 years. The outcome variable was "lack of knowledge about the HPV vaccine" and the explanatory variables were sociodemographic, behaviors, knowledge, and health conditions. Logistic regression model was used to calculate Odds Ratio (OR) and 95% confidence intervals (95%CI). Spatial analysis techniques were used to determine the formation of clusters in the federated units with similar proportions of adolescents who were unaware of the vaccine. The lack of knowledge about the HPV vaccine was reported by 45.54% of Brazilian students. There was a higher chance of lack of knowledge having had sexual intercourse (OR 1.43; 95% CI 1.20-1.70); attending public school (OR 1.72; 95%CI 1.47-2.02) and located in the Northeast Region (OR 1.35; 95%CI 1.08-1.69). The lower chance of lack of knowledge were female gender (OR 0.41; 95% CI 0.35-0.48), higher maternal education (OR 0.62; 95% CI 0.50-0.77) self-rated health as Poor/very poor (OR 0.64; 95% CI 0.49-0.86) and receiving contraceptive counseling (OR 0.77; 95% CI 0.65-0.91). The proportion of lack of knowledge about the HPV vaccine was higher with the formation of High-High spatial clusters in the states of Maranhão, Piauí, and Pernambuco. Sociodemographic, health, and behavioral conditions and knowledge of students, as well as school characteristics, were associated with lack of knowledge about the HPV vaccine. A higher frequency of lack of knowledge about the HPV vaccine among adolescents was found in the states of the Northeastern Region.