TABLE 1.

Characteristics of included studies

Author, year, country	Study design	Age of participants	Number of participants	Study population	Intervention	Follow‐up	HPV genotyping	Main results	Comments
Karimi‐Zarchi et al., 2020, Iran 28	Randomized controlled trial	21–45 years	312: 154 in control group and 158 in vaccination group	Women treated for histologically confirmed residual/recurrent CIN1 or CIN2 or CIN3	Three doses of the quadrivalent HPV vaccine. Women were excluded if they received only one dose	2 years	No	Vaccine efficacy: CIN1: 54.9%. CIN2: 63.3%. CIN3: 52.3% Total for CIN1‐3: 58.7%	Vaccine efficacy measured as difference in attack rate between vaccinated and nonvaccinated. The study did not distinguish between recurrent and residual disease
Pieralli et al., 2018, Italy 29	Randomized controlled trial	Under 45 years of age	178: 89 in control group and 89 in vaccination group	Women treated for CIN, any grade	Three doses of the quadrivalent HPV vaccine	At least 3 years	HPV genotyping if recurrence occurred. No HPV status of primary lesion available	Recurrence of LSIL/HSIL (in cervix, vulva and vagina) was 3.4% in vaccinated group vs 13.5% in the nonvaccinated group	Persistent disease 3 months after treatment was an exclusion criterion
Ghelardi et al., 2018, Italy 13	Observational study	18–45 years	524: 276 in control group and 248 in vaccination group	Women treated with LEEP for histologically confirmed CIN2+ or cervical cancer stage IA1	Three doses of the quadrivalent HPV vaccine.	Median 36 months (range 6–48 months)	HPV test and genotyping during the follow‐up program	Risk reduction of 81.2% (95% CI 34.3–95.7) in recurrence of CIN2+	CIN2+ independent of HPV type. Persistent histologically confirmed disease at 6‐month follow‐up visit was an exclusion criterion
Kang et al., 2013, Korea 12	Observational study	20–45 years	737: 377 in control group and 360 in vaccination group	Women treated with LEEP for CIN2–3	Three doses of the quadrivalent HPV vaccine	Median 3.5 years	Before LEEP and at every visit after LEEP HPV DNA test was performed	Hazard ratio of risk of recurrence of CIN2‐3 in women not receiving the vaccine vs women receiving the vaccine: 2.84 (1335–6042) P < 0.01	CIN2 or CIN3 at 3‐month follow‐up visit was considered as residual disease and patients were excluded
Sand et al., 2019, Denmark 14	Observational study	17–51 years	17 128 women: 15 054 in control group and 2074 in vaccination group, of which 399 were vaccinated 0–3 months before excisional treatment and 1675 were vaccinated 0–12 months after excisional treatment	Women treated with excisional treatment for CIN3	HPV vaccination (not further specified)	At least 3 years	No	Adjusted hazard ratio of risk of recurrent CIN2+ in women vaccinated 0–12 months after excisional treatment: 0,88 (95% CI 0.67–1.14)	Follow‐up began 1‐year post‐treatment to ensure only women with recurrent and not residual disease were included in the analysis
Ortega‐Quinonero et al., 2018, Spain 30	Observational study	18–65 years	242: 139 in control group and 103 in vaccination group	Women treated with LEEP for CIN2–3	Bivalent or quadrivalent HPV vaccination, number of doses not specified	2 years	HPV testing and determination of genotype both before treatment and during follow‐up	Recurrence of CIN2‐3 in vaccinated group was 4.8% vs 15.8% in the nonvaccinated	Residual disease, defined as a histological diagnosis of CIN2‐3 in biopsies three months after LEEP, was an exclusion criterion
Petrillo et al., 2020, Italy 31	Observational study	32–47 years	285: 103 in control group and 182 in vaccination group	Women treated with LEEP due to CIN.	Bi‐ or quadrivalent HPV vaccination, number of doses not specified	2 years	HPV testing before treatment, but not systematically at time of relapse	Odds ratio of disease recurrence: 0.4 (95% CI 0.2–0.8, P = 0,02) in vaccinated vs nonvaccinated	Outcome was defined as a cervical lesion of any histologic type (CIN1–3). No distinction between recurrent and residual disease
del Pino et al., 2020, Spain 32	Observational study	26–64 years	265. 112 in control group. 153 in vaccination group	Women treated with excisional treatment for CIN	Three doses of the bi‐, quadri‐ or nonavalent HPV vaccine. Women who received less than three doses were not excluded	At least 2 years	HPV testing both at enrolment and during follow‐up	Adjusted odds ratio of persistent/recurrent HSIL: 0.2 (95% CI 0.1–0.7) in vaccinated vs nonvaccinated	No distinction between residual and recurrent disease was made. 42.3% of the women showed either HSIL or LSIL at the first post‐treatment visit after 6 months
Bogani et al, 2020, Italy 33	Observational study.	24–44 years	300 in the propensity score‐matched comparison. 200 in control group. 100 in vaccination group	Women treated with LEEP for CIN2 or CIN3	Three doses of the bi‐ or quadrivalent HPV vaccine. Women who received less than three doses were not excluded	5 years	HPV testing before and after treatment. No information on HPV type was not an exclusion criterion	Recurrence of HSIL in vaccinated group was 0% vs 4,5% (n = 9) in control group. Not statistically significant.	No information on whether women in control group had previously received the HPV vaccine. Differentiation between residual and recurrent disease in the statistical analysis

Abbreviations: CIN, cervical intraepithelial lesion; HPV, human papillomavirus; HSIL, high‐grade squamous intraepithelial lesion; LEEP, loop electrosurgical excision procedure; LSIL, low‐grade squamous intraepithelial lesion.