Figure 1.

(A) Scatter plots of age when male students first had sex and age when male students would be willing to take HPV vaccination. Horizontal axis: age when male students first had sex. Vertical axis: age when male students would take HPV vaccination. Each hallow circle, rectangle and triangle represents an individual which could overlap. The diagonal dashed line is an artificial line that simulates the scenario when male students first had sex equals to age when they would take HPV vaccination. No one was less than 10 years old for first sex. (B) Scatter plots of age when female students first had sex and age when female students would be willing to take HPV vaccination. Horizontal axis: age when male students first had sex. Vertical axis: age when male students would take HPV vaccination. Each hallow circle, rectangle and triangle represents an individual which could overlap. The diagonal dashed line is an artificial line that simulates the scenario when female students first had sex equals to age when they would take HPV vaccination. No one was less than 10 years old for first sex.