Table 2

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

Effectiveness	Strata	No of estimates	Pooled VE (95% CI)	Prediction interval of VE (%)	Publication bias	Quality of evidence (GRADE)*
Overall		21	69.5% (54.7% to 79.5%)	<0–92.4	Detected	⨀⨀⨀⨁ very low
Stratified by	Timing of immunisation
	Post-excision	12	78.1% (68.7% to 84.7%)	67.1–85.4	Undetected	⨁⨀⨁⨁ moderate
	Pre-excision or pre/post-excision	5	47.8% (14.0% to 68.3%)	<0–88.5	Detected	⨀⨀⨀⨀ very low
	Previously immunised	4	49.8% (−45.5% to 82.7%)	<0–98.9	Detected	⨁⨀⨀⨀ very low
	HPV vaccine
	HPV2	4	48.4% (−55.0% to 82.8%)	<0–99.0	Undetected	⨁⨀⨀⨀ very low
	HPV4+	14	75.9% (58.3% to 86.1%)	<0–96.0	Detected	⨀⨀⨀⨁ very low
	Unspecific	3	59.8% (32.1% to 76.3%)	<0–98.7	Undetected	⨁⨁⨀⨀ low
	Follow-up duration
	≤2 years	5	72.3% (17.5% to 90.7%)	<0–99.2	Detected	⨀⨀⨀⨀ very low
	3–4 years	10	68.4% (53.9% to 78.3%)	50.8–79.7	Undetected	⨁⨁⨀⨁ moderate
	≥5 years	6	70.1% (53.7% to 80.6%)	44.4–83.9	Undetected	⨁⨁⨀⨁ moderate
	Study type
	Cohort	12	65.4% (45.4% to 78.1%)	<0–91.0	Undetected	⨁⨀⨀⨁ low
	Case–control	2	91.2% (46.9% to 98.6%)	<0–100	Detected	⨀⨀⨀⨁ very low
	Clinical trial	7	68.0% (41.8% to 82.4%)	<0–91.0	Undetected	⨁⨀⨀⨁ low
	Risk of bias
	Low	15	70.3% (60.6% to 77.7%)	59.4–78.3	Undetected	⨁⨁⨁⨁ high
	Moderate	6	69.0% (20.2% to 87.9%)	<0–98.1	Detected	⨀⨀⨀⨀ very low
Specific†		9	76.3% (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.