Efficacy of amoxicillin/clavulanic acid after surgical drainage of perianal abscess in the prevention of the development of anal fistula (PERIQxA study): study protocol for a multicenter randomized, double-blind clinical trial.

BACKGROUND: Anorectal fistula, which is a relatively common pathology, is the chronic manifestation of the acute perirectal process that forms an anal abscess. The development of a fistula after incision and drainage of an anal abscess is seen in approximately 26-37%. Its treatment is a relevant topic, and the role of the use of antibiotic therapy in its prevention remains controversial, after the publication of several studies with contradictory results and several methodological limitations. Our hypothesis is that the combination of amoxicillin and clavulanic acid will reduce the incidence of anal fistula. METHOD: The aim of this study is to evaluate the efficacy of antibiotherapy after surgical drainage of perianal abscess in the development of perianal fistula. The PERIQxA study is a multicenter, randomized, double-blind controlled trial. The study has been designed to include 286 adult patients who will be randomly (1:1) assigned to either the experimental (amoxicillin/clavulanic acid 875/125 mg TDS for 7 days) or the control arm (placebo). The primary outcome measure is the percentage of patients that develop perianal fistula after surgery and during follow-up (6 months). DISCUSSION: This clinical trial is designed to evaluate the efficacy and safety of amoxicillin/clavulanic in the prevention of perianal fistula. The results of this study are expected to contribute to stablish the potential role of antibiotherapy in the therapeutics for anal abscess. TRIAL REGISTRATION: EudraCT Number: 2021-003376-14. Registered on November 26, 2021.

The Optimal Primary Treatment for Pediatric Perianal Abscess and Anal Fistula: A Systemic Review and Meta-Analysis.

BACKGROUND: Perianal abscesses and anal fistulas are common. The principle of intention-to-treat has not been considered in previous systemic reviews. Thus, the comparison between primary and post-recurrence management was confused, and the recommendation of primary treatment is obscure. The current study aims to identify the optimal initial treatment for pediatric patients. METHODS: Using PRISMA guidelines, studies were identified from MEDLINE, EMBASE, PubMed, Cochrane Library, and Google Scholar without any language or study design restriction. The inclusion criteria include original articles or articles with original data, studies of management for a perianal abscess with or without anal fistula, and patient age of <18 years. Patients with local malignancy, Crohn's disease, or other underlying predisposing conditions were excluded. Studies without analyzing recurrence, case series of <5, and irrelevant articles were excluded in the screening stage. Of the 124 screened articles, 14 articles had no full texts or detailed information. Articles written in a language other than English or Mandarin were translated by Google Translation first and confirmed with native speakers. After the eligibility process, studies that compared identified primary managements were then included in the qualitative synthesis. RESULTS: Thirty-one studies involving 2507 pediatric patients met the inclusion criteria. The study design consisted of two prospective case series of 47 patients and retrospective cohort studies. No randomized control trials were identified. Meta-analyses for recurrence after initial management were performed with a random-effects model. Conservative treatment and drainage revealed no difference (Odds ratio [OR], 1.222; 95% Confidential interval [CI]: 0.615-2.427, p = 0.567). Conservative management had a higher risk of recurrence than surgery without statistical significance (OR 0.278, 95% CI: 0.109-0.707, p = 0.007). Compared with incision/drainage, surgery can prevent recurrence remarkably (OR 4.360, 95% CI: 1.761-10.792, p = 0.001). Subgroup analysis of different approaches within conservative treatment and operation was not performed for lacking information. CONCLUSION: Strong recommendations cannot be made due to the lack of prospective or randomized controlled studies. However, the current study based on real primary management supports initial surgical intervention for pediatric patients with perianal abscesses and anal fistula to prevent recurrence. LEVEL OF EVIDENCE: Type of study: Systemic review; Evidence level: Level II.

Vaccine Effectiveness Against 12-Month Incident and Persistent Anal Human Papillomavirus Infection Among Gay, Bisexual, and Other Men Who Have Sex With Men.

BACKGROUND: Real-world evidence of human papillomavirus (HPV) vaccine effectiveness (VE) against longitudinal outcomes is lacking among gay, bisexual, and other men who have sex with men (GBM). We compared 12-month incidence and persistence of anal HPV infection between vaccinated and unvaccinated GBM. METHODS: We recruited GBM aged 16-30 years in Montreal, Toronto, and Vancouver, Canada, from 2017 to 2019. Participants were followed over a median of 12 months (interquartile range, 12-13 months). Participants self-reported HPV vaccination and self-collected anal specimens for HPV DNA testing. We calculated prevalence ratios (PR) for 12-month cumulative incidence and persistence with ≥1 quadrivalent vaccine type (HPV 6/11/16/18) between vaccinated (≥1 dose at baseline) and unvaccinated participants using a propensity score-weighted, modified Poisson regression. RESULTS: Among 248 participants, 109 (44.0%) were vaccinated at baseline, of whom 62.6% received 3 doses. PRs for HPV 6/11/16/18 were 0.56 (95% confidence interval [CI], .24-1.31) for cumulative incidence and 0.53 (95% CI, .25-1.14) for persistence. PRs were 0.23 (95% CI, .05-1.03) and 0.08 (95% CI, .01-.59) for incidence and persistence, respectively, among participants who received their first dose at age ≤23 years and 0.15 (95% CI, .03-.68) and 0.12 (95% CI, .03-.54) among participants who were sexually active for ≤5 years before vaccination. CONCLUSIONS: Findings support national recommendations for HPV vaccination at younger ages or soon after sexual debut.

Incidence and clearance of anal high-risk Human Papillomavirus infection and their risk factors in men who have sex with men living with HIV.

HIV-infected men who have sex with men (MSM) display the highest prevalence of anal infection by high-risk Human Papillomaviruses (hrHPVs) and incidence of anal carcinoma. Anal specimens were genotyped by the Linear Array. Incidence and clearance of anal infection by hrHPVs, hrHPVs other than HPV16, low-risk HPVs, and four individual types (6,11,16,18) were estimated using a two-state Markov model. Determinants for incidence and clearance were assessed by logistic regression. Overall, 204 individuals were included (median age 42 years, IQR = 34-49). For hrHPVs, incidence and clearance rates were 36.1 × 1000 person-months (p-m) (95% CI 23.3-56.5) and 15.6 × 1000 p-m (95% CI 10.7-23.3), respectively. HPV16 showed a higher incidence than HPV18 (10.2 vs. 7.2 × 1000 p-m). Its clearance was more than twofold lower than that of HPV18 (30.1 vs. 78.2 × 1000 p-m). MSM receiving cART displayed a 68% to 88% decrease in risk of acquiring hrHPVs, hrHPVs other than HPV16, HPV16, and HPV18 (adjusted Hazard Ratio [aHR] 0.13, 95% CI 0.02-0.67; aHR 0.22, 95% CI 0.06-0.78; aHR 0.32, 95% CI 0.12-0.90; aHR 0.12, 95% CI 0.04-0.31, respectively) than patients not treated. A nadir CD4 + count < 200 cells/mm3 significantly reduced the clearance of hrHPVs other than HPV16 (aHR 0.39, 95% CI 0.17-0.90). cART use reduces the risk of acquiring anal infection by hrHPVs.

Time-trend of hospitalizations for anogenital warts in Veneto region in the HPV vaccination era: a cross sectional study (2007-2018).

BACKGROUND: Human papillomavirus (HPV) is a common sexually transmitted pathogen and the cause of several cancers and of anogenital warts. With this study, we estimated the trend of hospitalizations for anogenital warts (AGWs) in the Veneto region (Italy) from 2007 to 2018. METHODS: The analysis included all the hospital discharge records of public and accredited private hospitals occurred in Veneto residents in the timespan 2007-2018. The ICD9-CM code 078.11 considered were those associated with condyloma acuminatum and those associated with surgical interventions for vulval/vaginal warts, penile warts anal warts. Annual total and sex- and age-specific hospitalization rates and trends were calculated and correlated with the different HPV vaccine coverage over the study period. RESULTS: We observed an overall reduction of hospitalization rates for AGWs: from 15.0 hospitalizations every 100,000 Veneto residents in years 2007-08 to 10.9 hospitalizations every 100,000 Veneto residents in year 2017-18 (- 37.4%; p < 0.05). Reduction has been caused by a drop in hospitalizations in females - from a rate of 20.4/100,000 in 2007-2008 to a rate of 10.8/100,000 in 2017-18 (AAPC: -7.1; 95%CI: - 10.6;-3.4); while in males, we observed a slight - but not statistically significant - increase in hospitalization rates. CONCLUSION: The marked decline in hospitalization rates for AGWs in Veneto Region is probably attributable to the high coverage rates of HPV vaccination programs implemented since 2008.

Vaccine Effectiveness Against Prevalent Anal and Oral Human Papillomavirus Infection Among Men Who Have Sex With Men-United States, 2016-2018.

BACKGROUND: In the United States, human papillomavirus (HPV) vaccination has been recommended for young adult men who have sex with men (MSM) since 2011. METHODS: The Vaccine Impact in Men study surveyed MSM and transgender women aged 18-26 years in 3 US cities during 2016-2018. Self-collected anal swab and oral rinse specimens were assessed for 37 types of HPV. We compared HPV prevalence among vaccinated and unvaccinated participants and determined adjusted prevalence ratios (aPR) and 95% confidence intervals (CI). RESULTS: Among 1767 participants, 704 (39.8%) self-reported receiving HPV vaccine. Median age at vaccination (18.7 years) was older than age at first sex (15.7 years). Quadrivalent vaccine-type HPV was detected in anal or oral specimens from 475 (26.9%) participants. Vaccine-type HPV prevalence was lower among vaccinated (22.9%) compared with unvaccinated (31.6%) participants; aPR for those who initiated vaccination at age ≤18 years was 0.41 (CI, 0.24-0.57) and at age >18 years was 0.82 (CI, 0.67-0.98). Vaccine effectiveness of at least 1 HPV vaccine dose at age ≤18 years or >18 years was 59% and 18%, respectively. CONCLUSIONS: Findings suggest real-world effectiveness of HPV vaccination among young adult MSM. This effect was stronger with younger age at vaccination.

Risk of Anal Cancer Following Benign Anal Disease and Anal Cancer Precursor Lesions: A Danish Nationwide Cohort Study.

BACKGROUND: Human papillomavirus (HPV) is associated with the majority of anal high-grade intraepithelial neoplasia (AIN) and anal cancers. Little is known about the risk of anal cancer following a diagnosis of benign anal disease and AIN. METHODS: Using data from nationwide, population-based Danish registries, a cohort of 126,174 individuals with either non-neoplastic anal disease or AIN 1 to 3 during 1970 to 2016 was followed until first occasion of anal cancer. Information on HIV status was obtained from the Danish HIV Cohort Study. The absolute risk of anal cancer was estimated using the Aalen-Johansen estimator taking into account censoring at emigration and end of follow-up and competing risk at time of death. Standardized incidence ratios (SIR) for anal cancer among individuals with non-neoplastic anal disease, including inflammatory lesions, hemorrhoids, and polyps, were estimated in Poisson models. Sex-, age-, and calendar period-specific national population rates were estimated using the Danish National Pathology Registry. RESULTS: Anal cancer risk increased with increasing severity of lesions, reaching 4% 5 years after diagnosis of AIN3. Even among those with non-neoplastic anal lesions, particularly inflammatory lesions, anal cancer risk was significantly higher than expected from Danish national anal cancer rates (SIR = 2.8; 95% confidence intervals, 2.3-3.2). The absolute 5-year risk of anal cancer following AIN3 was considerably higher among HIV-positive (14.1%) than HIV-negative (3.2%) individuals. CONCLUSIONS: Anal cancer risk increases with increasing severity of lesions and is especially high among HIV-positive individuals. IMPACT: Vaccination against HPV is important in the prevention of both high-grade AIN and anal cancer.

The effectiveness of digital anal dilatation in preventing anal strictures after anorectal malformation repair.

BACKGROUND: Anal dilatation is performed after repair of anorectal malformations(ARMs) and is vital in prevention of anal stricture formation. The ideal protocol utilizes Hegar dilators. In our setup, few parents will acquire Hegar dilators for home based anal dilatation but majority will use fingers as an alternative. The basis of this study was to determine the effectiveness of digital anal dilatations in preventing anal strictures. MATERIALS AND METHODS: This was a descriptive cross-sectional study carried out at Kenyatta National Hospital (KNH) which recruited children post ARM repair undergoing digital anal dilatation. The diameters of the digits used for anal dilatation were assessed for adequacy using the desired anal size as a reference point. The main outcome variable was the presence of anal strictures. Data were entered in a data collection sheet and analyzed by use of SPSS (V.21.0 Chicago, Illinois). Chi-square test and Fisher's exact test were used to ascertain association among variables. A P-value of less than 0.05 was considered statistically significant. RESULTS: 50 patients with ARM post repair were recruited in the study. The rate of occurrence of anal stricture was 22%. Among the participants with anal strictures, only 27% were compliant to the dilatation regimen while 73% reported noncompliance. The mean diameter(mm) of the dilating digits at the level of the middle phalanx was Index finger (15.4 ±â€¯0.58), middle finger (15.2 ±â€¯0.61), ring finger (14.2 ±â€¯0.71), small finger (12.5 ±â€¯0.91) and thumb (17.6 ±â€¯0.78). 46% of the participants were dilated with appropriately sized digits. The remainder had dilatations done with larger (22%) or smaller digits (32%). Notably, anal strictures occurred in participants who were dilated with inappropriately sized digits (P = 0.001). CONCLUSION: Digital anal dilatation is safe and effective as a mode of anal dilation in the setting of compliance to a strict dilatation protocol, daily frequency of dilations and use of appropriately sized digits. Owing to the variability in the finger size, we recommend that digits be calibrated and education given to the caregivers on the use of the appropriately sized digit. LEVEL OF EVIDENCE: Treatment study. Level III.

Trends in anogenital wart incidence among Tennessee Medicaid enrollees, 2006-2014: The impact of human papillomavirus vaccination.

INTRODUCTION: Evidence of human papillomavirus (HPV) vaccine impact on anogenital warts (AGWs) by race or urbanicity in the US is lacking. We evaluated HPV vaccine impact in Tennessee by assessing AGW trends among Tennessee Medicaid (TennCare) enrollees aged 15-39 years from 2006-2014. METHODS: Persons with incident AGWs were identified using diagnosis/pharmacy codes from TennCare billing claims. We calculated sex-specific annual AGW incidence by age group, race, and urbanicity; estimated annual percent changes (APCs) using log-linear models; and performed pairwise comparisons by race and urbanicity. RESULTS: AGW incidence decreased among females aged 15-19 (APC = -10.6; P < 0.01) and 20-24 years (APC = -3.9; P = 0.02). Overall trends were similar between Whites and Blacks, and between those living in metropolitan statistical areas (MSAs) and non-MSAs. Rates among males aged 15-19 years began decreasing after 2010. Among enrollees aged 25-39 years, rates increased or were stable. CONCLUSIONS: Following introduction of the HPV vaccine in 2006, AGWs decreased among age groups most likely to be vaccinated. The change in trend among young males after 2010 suggests early herd effects. Our findings indicate vaccine effects and support the importance of improving adherence to current vaccination recommendations for preventing AGWs and other HPV-related diseases.

Incision & drainage of perianal sepsis in the immunocompromised: A need for heightened postoperative awareness.

BACKGROUND: Incision and drainage of perianal sepsis has appreciable success in the immunocompetent population, but outcomes after incision and drainage in the immunosuppressed population are unknown. METHODS: 13,666 patients (n = 930 immunosuppressed) undergoing incision and drainage of perianal sepsis between 2011 and 2015 in the American College of Surgeons National Surgical Quality Improvement Program were identified. The main outcomes were major morbidity, return to the operating room, and mortality. Multivariable analysis was performed for each outcome. RESULTS: Sepsis was the most common postoperative complication. Preoperative immunosuppression was an independent risk factor for major morbidity (odds ratio [OR]: 1.6, p < 0.01), return to the operating room (OR: 1.9, p < 0.01), and mortality (OR: 2.6, p < 0.01). CONCLUSIONS: Immunosuppression is an independent risk factor for major morbidity, return to the operating room, and mortality. With post-operative sepsis the most common complication, inpatient admission and extended duration antibiotic therapy is warranted in immunosuppressed patients.

Systematic review and evidence synthesis of non-cervical human papillomavirus-related disease health system costs and quality of life estimates.

BACKGROUND: Many economic evaluations of human papillomavirus vaccination should ideally consider multiple disease outcomes, including anogenital warts, respiratory papillomatosis and non-cervical cancers (eg, anal, oropharyngeal, penile, vulvar and vaginal cancers). However, published economic evaluations largely relied on estimates from single studies or informal rapid literature reviews. METHODS: We conducted a systematic review of articles up to June 2016 to identify costs and utility estimates admissible for an economic evaluation from a single-payer healthcare provider's perspective. Meta-analyses were performed for studies that used same utility elicitation tools for similar diseases. Costs were adjusted to 2016/2017 US$. RESULTS: Sixty-one papers (35 costs; 24 utilities; 2 costs and utilities) were selected from 10 742 initial records. Cost per case ranges were US$124-US$883 (anogenital warts), US$6912-US$52 579 (head and neck cancers), US$12 936-US$51 571 (anal cancer), US$17 524-34 258 (vaginal cancer), US$14 686-US$28 502 (vulvar cancer) and US$9975-US$27 629 (penile cancer). The total cost for 14 adult patients with recurrent respiratory papillomatosis was US$137 601 (one paper).Utility per warts episode ranged from 0.651 to 1 (12 papers, various utility elicitation methods), with pooled mean EQ-5D and EQ-VAS of 0.86 (95% CI 0.85 to 0.87) and 0.74 (95% CI 0.74 to 0.75), respectively. Fifteen papers reported utilities in head and neck cancers with range 0.29 (95% CI 0.0 to 0.76) to 0.94 (95% CI 0.3 to 1.0). Mean utility reported ranged from 0.5 (95% CI 0.4 to 0.61) to 0.65 (95% CI 0.45 to 0.75) (anal cancer), 0.59 (95% CI 0.54 to 0.64) (vaginal cancer), 0.65 (95% CI 0.60 to 0.70) (vulvar cancer) and 0.79 (95% CI 0.74 to 0.84) (penile cancer). CONCLUSIONS: Differences in values reported from each paper reflect variations in cancer site, disease stages, study population, treatment modality/setting and utility elicitation methods used. As patient management changes over time, corresponding effects on both costs and utility need to be considered to ensure health economic assumptions are up-to-date and closely reflect the case mix of patients.

The clinical and therapeutic approach to anal stenosis.

Anal stenosis is a fibrous narrowing of the anal channel. It develops, in most cases, in the aftermath of proctologic surgical procedures with extensive anoderm excision or in the presence of chronic anal inflammation in patients with Crohn Disease. However rare, this condition is thoroughly debilitating for the patients. Symptoms include constipation, pain and bleeding with defecation and a reduction of the caliber of stools. Diagnosis is essentially clinical. Prevention of postsurgical stenosis is based on a scrupulous surgical technique and on an extensive and carefully- planned follow up. Treatment is based on an initially conservative approach with regularization of stool transit through hydration, dietary fibers and bulk-forming laxatives. The role of mechanical dilatation in the treatment of AS is still debated. For severe cases and cases that are not responsive to conservative treatment we must resort to surgery. Surgical approach is tailored on the severity, position and extension. The most severe cases require anoplasty procedures with mucosal or anal flaps. KEY WORDS: Anal stenosis, Anal stricture,Proctology.

Vaccine-preventable anal infections by human papillomavirus among HIV-infected men who have sex with men.

AIM: HIV-infected men who have sex with men (MSM) show the highest prevalence of anal HPV infection. Anal prevalence of the HPVs targeted by the quadrivalent HPV vaccine (4vHPV) and nonavalent HPV vaccine (9vHPV) was estimated in this population. MATERIALS & METHODS: Anal specimens were collected from HIV-infected MSM attending a sexually transmitted infection/HIV center. Specimens were analyzed using the Linear Array HPV Genotyping Test. RESULTS: A total of 49.5 and 71.2% of the 313 enrolled MSM harbored at least one of the 4vHPV and 9vHPV types, respectively. A significantly decreasing trend was observed for the prevalence of both 4vHPV (p = 0.04) and 9vHPV types (p < 0.001) across age classes. CONCLUSION: A substantial proportion of HIV-infected MSM do not harbor a current anal infection with vaccine-preventable HPVs. The potential benefit of the 4vHPV versus 9vHPV vaccination in these subjects, including older MSM, should be investigated.

The Impact of Varying Numbers of Quadrivalent Human Papillomavirus Vaccine Doses on Anogenital Warts in the United States: A Database Study.

OBJECTIVE: The aim of the study was to investigate the effects of 3 or less quadrivalent human papillomavirus (HPV) vaccine doses on anogenital warts in both males and females in the United States. MATERIALS AND METHODS: We conducted a retrospective database study that included males and females aged 9 to 26 years who received varying numbers of vaccine doses between 2006 and 2015. The primary outcome was the incidence of anogenital warts starting 3 months after the last dose of the HPV vaccine. Proportional hazard regression models were used to examine the association between the number of HPV vaccine doses and the incidence of anogenital warts. The Kaplan-Meier method was used to estimate the proportion of subjects. RESULTS: A total of 440,532 females and 133,394 males were included in the study. We found a significant 2-way interaction (p < .0001) between the number of doses and age. For the group between 15 and 19 years of age, the hazard ratio of anogenital warts for the 3-dose vaccine was 0.58 (95% CI = 0.49-0.70), whereas it was 0.65 (95% CI = 0.49-0.85) and 0.67 (95% CI = 0.51-0.89) for the 1- and 2-dose groups, respectively. CONCLUSIONS: Our findings showed that 1, 2, and 3 doses of the quadrivalent HPV vaccine were similarly effective against anogenital warts in 15- to 19-year-old adolescents, irrespective of sex.

Minimization of the perianal infection rate of hematological malignancies with agranulocytosis by quality control circle activity and patient-hospital-student win-win concept.

Objective The agranulocytosis-associated perianal infection (PI) rate ranges from 60% to 100% among patients with hematopoietic malignancies. In this study, we assessed the efficacy of a quality control circle (QCC) to minimize the PI rate. Methods Among 274 patients with severe immunodeficiency (agranulocytosis of ≥2 weeks) in our bone marrow transplantation center, the PI rate was 17.20%. A QCC was established following the 10 steps of the plan-do-check-act (PDCA) model; this was scientifically supported by culturing the bacterial colony from patients' perianal skin to determine the sanitization effect and interval time. Because a warm aqueous solution of potassium permanganate is recommended for sanitization, the bacterial colony culture was also used to determine the proper drug concentration, water temperature, and soaking time. All procedures were standardized. Patients, hospital staff, and medical students were enrolled into the QCC team based on the patient-hospital-student (PHS) win-win concept. Results After establishment of the PDCA model, the PI rate among 253 patients decreased from 17.20% to 5.93% and remained at 5.25% during the following year. The medical expenses and length of hospital stay consequently decreased. Conclusion The QCC and PHS win-win concept can reduce the PI rate and promote medical quality.

Effect of naturally acquired type-specific serum antibodies against human papillomavirus type 16 infection.

BACKGROUND: While vaccine-induced antibodies are known to confer protection against incident human papillomavirus (HPV) infection, there is inconsistent data regarding the protective effect of naturally acquired anti-HPV antibodies. OBJECTIVES: To estimate the protective effect of naturally acquired anti-HPV16 serum antibodies against incident anogenital infection with HPV16 in females aged 20-64 years and to assess whether antibodies influence the persistence/clearance of anogenital HPV16 infection. STUDY DESIGN: 4432 women attending the organized national cervical cancer screening program in Slovenia were initially enrolled. 2199 and 1848 women had valid HPV DNA results obtained using PCR-based assays and HPV antibody serotyping results obtained using pseudovirion-based serological assay, at baseline and at three-year follow-up, respectively. RESULTS: Baseline HPV16 seroprevalence was 2.4-fold higher among HPV16 DNA-positive women (55.7% vs. 23.2%; p<0.01). Baseline HPV16 DNA-positive/seronegative women frequently acquired anti-HPV16 antibodies during follow-up (OR=8.2; 95% CI: 3.8-17.8). Baseline anti-HPV16 antibodies persisted at follow-up, irrespective of baseline HPV16 DNA status (OR=40.6; 95% CI: 30.3-54.5). Baseline HPV16 DNA-negative/seropositive women were less likely to acquire HPV16 infection at follow-up (unadjusted OR=0.2; 0.1-0.9). However, the age-adjusted association was non-significant (adjusted OR=0.3; 0.1-1.2). The tendency for protective effect was stronger among women older than 25 years (OR=0.2; 0.03-1.8). Baseline anti-HPV16 antibodies were not associated with persistence/clearance of HPV16 infection at follow-up (OR=0.8; 0.3-1.9). CONCLUSIONS: Naturally acquired anti-HPV16 serum antibodies appeared to protect against anogenital HPV16 infection, but this association was at least partially confounded by age. Baseline anti-HPV16 serum antibodies did not influence persistence/clearance of HPV16 infection at follow-up.

Human papillomavirus vaccine efficacy in the prevention of anogenital warts: systematic review and meta-analysis.

OBJECTIVE:: To review evidence on the efficacy of HPV vaccines in the prevention of non-cancer lesions (anogenital warts [AGW], recurrent laryngeal papillomatosis and oral papillomatosis). MATERIALS AND METHODS:: We conducted a systematic review of randomized trials. We performed random effect models and effects were reported as relative risks (RR) and their confidence intervals (95%CI) following both intention to treat (ITT) and per protocol (PP) analyses. RESULTS:: We included six studies (n=27 078). One study was rated as high risk of bias. One study could not be included in the meta-analysis because it provided combined results. We found that quadrivalent vaccine reduced the risk of AGW by 62% (RR: 0.38, 95%CI:0.32-0.45, I2:0%) in the ITT analysis and by 95% (RR: 0.05, 95%CI:0.01-0.25, I2:66%) in the PP analysis. Subgroup analyses of studies in women or with low-risk of bias provided similar results. CONCLUSION:: HPV quadrivalent vaccine is efficacious in preventing AGW in men and women.