Estimated crude incidence rates and HRs for time to HIV by the quintiles of age at first sex
| Crude incidence rate per 100 person-years (95% CI) | Unadjusted HR (95% CI) | p Value | Adjusted HR* (95% CI) | p Value | |
| Age at first sex (years) | |||||
| <15 | 12.0 (8.0 to 18.0) | 1.97 (1.07 to 3.63) | 0.029 | 1.78 (0.96 to 3.29) | 0.066 |
| 15–16 | 7.2 (5.7 to 9.0) | 1.11 (0.69 to 1.80) | 0.664 | 0.90 (0.53 to 1.46) | 0.633 |
| 17–18 | 6.1 (4.1 to 9.0) | 0.95 (0.53 to 1.69) | 0.851 | 0.82 (0.45 to 1.47) | 0.496 |
| 19–20 | 5.1 (2.9 to 9.0) | 0.78 (0.39 to 1.60) | 0.503 | 0.72 (0.35 to 1.67) | 0.365 |
| 21+ | 6.4 (4.2 to 9.8) | 1 | 1 | ||
↵* Adjusted for age, number of lifetime sex partners, cohabitation status, level of education, ever used condom with vaginal sex.