Table 4.
HPV16 and HPV18 vaccine efficacies by antibody titer among individuals with evidence of a previous* HPV16 or HPV18 infection prior to vaccination
| Population | Arm | No. women | No. events* | HPV16/18 prev., % | Efficacy (95% CI), % |
|---|---|---|---|---|---|
| HPV16 seropositive and cervical HPV16 DNA negative at baseline | |||||
| Cervical, anal, or oral HPV16 | HPV vaccine | 477 | 15 | 3.1 | 47.7 (3.2 to 72.7) |
| Multisite woman level† | Control | 482 | 29 | 6.0 | |
| Cervical HPV16 | HPV vaccine | 477 | 5 | 1.0 | 71.9 (27.4 to 90.7) |
| Control | 482 | 18 | 3.7 | ||
| HPV16 titer below the median titer (<32 EU/mL) | |||||
| Cervical, anal, or oral HPV16 | HPV vaccine | 247 | 4 | 1.6 | 73.4 (25.3 to 92.3) |
| Multisite woman level‡ | Control | 279 | 17 | 6.1 | |
| Cervical HPV16 | HPV vaccine | 247 | 3 | 1.2 | 75.8 (21.9 to 94.4) |
| Control | 279 | 14 | 5.0 | ||
| HPV16 titer at or above the median titer (≥32 EU/mL) | |||||
| Cervical, anal, or oral HPV16 | HPV vaccine | 230 | 11 | 4.8 | 19.1 (-86.5 to 65.2) |
| Multisite woman level‡ | Control | 203 | 12 | 5.9 | |
| Cervical HPV16 | HPV vaccine | 230 | 2 | 0.9 | 55.9 (-148.8 to 94.3) |
| Control | 203 | 4 | 2.0§ | ||
| HPV18 seropositive and cervical HPV18 DNA negative at baseline | |||||
| Cervical, anal, or oral HPV18 | HPV vaccine | 509 | 8 | 1.6 | 47.8 (-22.3 to 79.0) |
| Multisite woman level‡ | Control | 498 | 15 | 3.0 | |
| Cervical HPV18 | HPV vaccine | 509 | 2 | 0.4 | 78.3 (8.7 to 96.8) |
| Control | 498 | 9 | 1.8 | ||
| HPV18 titer below the median titer (<17 EU/mL) | |||||
| Cervical, anal, or oral HPV18 | HPV vaccine | 249 | 2 | 0.8 | 81.0 (23.7 to 97.1) |
| Multisite woman level‡ | Control | 260 | 11 | 4.2 | |
| Cervical HPV18 | HPV vaccine | 249 | 0 | 0.0 | 100.0 (52.6 to 100.0) |
| Control | 260 | 8 | 3.1 | ||
| HPV18 titer at or above the median titer (≥17 EU/mL) | |||||
| Cervical, anal, or oral HPV18 | HPV vaccine | 260 | 6 | 2.3 | -37.3 (-451.8 to 62.4) |
| Multisite woman level‡ | Control | 238 | 4 | 1.7 | |
| Cervical HPV18 | HPV vaccine | 260 | 2 | 0.8 | -83.1 (-5300.3 to 86.1) |
| Control | 238 | 1 | 0.4|| | ||
* Defined as women who were human papillomavirus (HPV) 16 seropositive and cervical HPV16 DNA negative at baseline for the HPV16 analysis, and HPV18 seropositive and cervical HPV18 DNA negative at baseline for the HPV18 analysis. CI = confidence interval; HPV = human papillomavirus.
† For this analysis, events were defined as detection of type-specific HPV16 or HPV18 DNA at the four-year visit among women who were HPV16 or HPV18 seropositive for that same HPV type at baseline (ie, the analysis was restricted to examining the potential protection against the HPV type that the women previously had prior to vaccination).
‡ A woman-level event is defined as a woman who is positive for cervical, anal, and/or oral HPV DNA at the four-year visit. § Cervical HPV16 prevalence at the four-year visit among high-titer HPV16 seropositive/HPV16 DNA-negative individuals was not statistically significantly lower than the cervical HPV16 prevalence in the control arm of the naïve cohort (2.0% vs 5.1%, P = .06).
|| Cervical HPV18 prevalence at the four-year visit among high-titer HPV18 seropositive/HPV18 DNA-negative individuals was statistically significantly lower than the cervical HPV18 prevalence in the control arm of the naïve cohort (0.4% vs 3.2%, P = .02).