Table 2

Overall and stratified pooled vaccine effectiveness (VE) by the investigated variables including the prediction interval, publication bias and quality assessment studies

EffectivenessStrataNo of estimatesPooled VE (95% CI)Prediction interval of VE (%)Publication biasQuality of evidence (GRADE)*
Overall2169.5% (54.7% to 79.5%)<0–92.4Detected⨀⨀⨀⨁ very low
Stratified byTiming of immunisation
Post-excision1278.1% (68.7% to 84.7%) 67.1–85.4 Undetected⨁⨀⨁⨁ moderate
Pre-excision or pre/post-excision547.8% (14.0% to 68.3%)<0–88.5Detected⨀⨀⨀⨀ very low
Previously immunised449.8% (−45.5% to 82.7%)<0–98.9Detected⨁⨀⨀⨀ very low
HPV vaccine
HPV2448.4% (−55.0% to 82.8%)<0–99.0Undetected⨁⨀⨀⨀ very low
HPV4+1475.9% (58.3% to 86.1%)<0–96.0Detected⨀⨀⨀⨁ very low
Unspecific359.8% (32.1% to 76.3%)<0–98.7Undetected⨁⨁⨀⨀ low
Follow-up duration
≤2 years572.3% (17.5% to 90.7%)<0–99.2Detected⨀⨀⨀⨀ very low
3–4 years1068.4% (53.9% to 78.3%) 50.8–79.7 Undetected⨁⨁⨀⨁ moderate
≥5 years670.1% (53.7% to 80.6%) 44.4–83.9 Undetected⨁⨁⨀⨁ moderate
Study type
Cohort1265.4% (45.4% to 78.1%)<0–91.0Undetected⨁⨀⨀⨁ low
Case–control291.2% (46.9% to 98.6%)<0–100Detected⨀⨀⨀⨁ very low
Clinical trial768.0% (41.8% to 82.4%)<0–91.0Undetected⨁⨀⨀⨁ low
Risk of bias
Low1570.3% (60.6% to 77.7%) 59.4–78.3 Undetected⨁⨁⨁⨁ high
Moderate669.0% (20.2% to 87.9%)<0–98.1Detected⨀⨀⨀⨀ very low
Specific†976.3% (64.9% to 84.0%) 62.0–85.2 Undetected⨁⨁⨁⨁ high
  • *Limitation, inconsistency, indirectness, imprecision in the order listed in the table: ⨀—serious or ⨁—non-serious.

  • †Post-excision immunisation mostly with an HPV4+ vaccine followed up at least 3 years in studies at low risk of bias.

  • GRADE, Grading of Recommendations Assessment, Development, and Evaluation; HPV2/HPV4+, bivalent/quadrivalent or nonavalent human papillomavirus vaccine.