High-risk HPV status at study initiation	Risk with placebo	Risk with HPV vaccination	Number needed to treat (95% CI)	Number of participants (number of studies)	Quality of evidence
Negative
CIN 2	28.7 per 1,000	10.6 per 1,000	55 (46 to 77)	25,180 (5)	High
CIN 3	10.9 per 1,000	2.3 per 1,000	*	20,719 (3)	Moderate
CIN 2 and 3 combined	39.6 per 1,000	12.9 per 1,000	*	—	—
Irrespective of risk
CIN 2	55.9 per 1,000	39.1 per 1,000	59.5 (42 to 119)	35,779 (4)	High
CIN 3	26.6 per 1,000	17.8 per 1,000	113 (74 to 520)	35,489 (3)	Moderate
CIN 2 and 3 combined	82.5 per 1,000	56.9 per 1,000	39 (27 to 97)	—	—