ORIGINAL STUDY
Human Papillomavirus Vaccination and Cervical Cytology in Young Minority Women Susan B. Brogly, PhD, MSc,* Rebecca B. Perkins, MD, MSc,Þ Dimity Zepf, BS,þ Janina Longtine, MD,§ and Shi Yang, MD, MSc¶ Background: Continued surveillance of human papillomavirus (HPV) vaccination is necessary to identify clinical benefits, particularly given the low rate of vaccine uptake and completion and vaccination of many young women after sexual debut. We studied the effect of catch-up HPV vaccination on cervical cytology and HPV infection in sexually active, low-income and minority young women. Methods: We conducted a cross-sectional study of 235 women aged 21 to 30 years undergoing routine cervical cytology testing. Demographic and behavioral characteristics were self-reported. HPV vaccination status was determined by self-report and verified with electronic medical records. Liquid-based cytology samples were tested for HPV genotypes. Adjusted prevalence ratios between HPV vaccination and (1) abnormal cervical cytology result and (2) HPV genotype were estimated. Findings: At the time of the study, 96 women (41%) had received at least 1 HPV vaccination, 54 of whom had completed the series; 97% of women were vaccinated after sexual debut. Twenty-four (10%) women had an abnormal cervical cytology result. The prevalence of abnormal cytology was 65% lower in women who received at least 1 HPV vaccination versus unvaccinated women (adjusted prevalence ratio, 0.35; 95% confidence interval, 0.14Y0.89). Among 232 women with genotype results, 46 (20%; 95% confidence interval, 15%Y26%) had HPV infection detected. HPV types 16, 18, 45, 53, and 66 were most prevalent. Conclusions: The prevalence of abnormal cytology was lower in vaccinated versus unvaccinated women, despite receipt of vaccination after sexual debut. Continued assessment of HPV vaccine effectiveness before and after sexual debut on HPV infection and cervical dysplasia is needed.
T
he human papillomavirus (HPV) vaccine demonstrated high efficacy in preventing HPV infection and disease in women aged 16 to 26 years, with the highest efficacy against HPV types 16 and 18 in women without prior HPV infection.1,2 In the United States, routine vaccination with the quadrivalent HPV vaccine (HPV types 6, 11, 16, 18) is recommended for girls 11 to 12 years of age, and catch-up vaccination is recommended
From the *Department of Epidemiology, Boston University School of Public Health, Boston, MA; †Department of Obstetrics and Gynecology, Boston University School of Medicine, Boston, MA; ‡Department of Pathology, Brigham and Women’s Hospital, Boston, MA; §Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY; and ¶Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA
The authors thank the women for participating in this study. The authors are grateful to Sonya Kovacic and Dr Myrlene Jeudy for their assistance with patient recruitment and data collection. The authors thank Ron McGlennen at Access Genetics for subtyping software access. This study was funded by the American Cancer Society, ACS Grant IRG-72-001-35-IRG. Conflict of interest: None declared. Correspondence: Susan Brogly, PhD, MSc, Department of Epidemiology, Boston University School of Public Health, 715 Albany St, Talbot 419E, Boston, MA 02118. E-mail: [email protected]. Received for publication March 6, 2014, and accepted June 13, 2014. DOI: 10.1097/OLQ.0000000000000162 Copyright * 2014 American Sexually Transmitted Diseases Association All rights reserved.
Sexually Transmitted Diseases
&
for girls and women 13 through 26 years of age.3 Vaccine uptake and completion, however, has been low.4,5 In 2012, 54% of young girls initiated vaccination and 33% completed vaccination.6 The observed incomplete vaccination of low-income and minority women in the Unites States7 is particularly concerning because of the high rates of HPV infection and cervical cancer in these women.8,9 Additional surveillance of vaccine effectiveness of these women is needed.10Y12 We conducted a cross-sectional study of HPV vaccination and (1) cervical cytology and (2) HPV infection among lowincome, minority young women attending a large volume safety-net hospital clinic. We previously reported low vaccine uptake and completion in adolescents of this population.13
METHODS This study was conducted in an obstetrics and gynecology clinic of a safety-net hospital serving a low-income, minority population of inner-city Boston. Women 21 to 30 years of age who presented to the study clinic for a scheduled Papanicolaou (Pap) test from April 2011 to March 2012 were eligible for participation. Our selected age range for study participation was based on clinical care: (1) the HPV vaccine was implemented in 2007 for women 11 to 26 years of age, and thus, at the time of study enrollment, all participants had been eligible for vaccination in 2007 to 2011, and (2) because leftover clinical Pap test specimens were used in our study for HPV genotyping, we restricted the study to women 21 years or older who undergo routine Pap tests. All study participants signed an informed consent form in English or Spanish. Participants completed a short questionnaire on smoking status, HPV vaccination, age of first sexual intercourse, lifetime number of male sexual partners, and usual condom use with these male partners. Electronic medical records were used to supplement information on these variables and to obtain information on prior Pap test results. Participants received a US $5 pharmacy gift certificate as compensation for their time. This study was approved by the research review board of Boston University Medical Center. Cytology specimens were collected per routine clinical practice by using the Thinprep system; cytopathology slides were prepared for Pap test staining. The remaining collections were resuspended in 2 mL of buffer and used for HPV genotyping with the technician blinded to the Pap test result. DNA extraction was performed using the QIAgen QIAamp DNA Kit. The sample was centrifuged to a pellet cellular material, and the pellet was digested overnight with ATL (tissue lysis buffer) and proteinase K. DNA quality was assayed by polymerase chain reaction (PCR) amplification of A-globin (500-base-pair product) concurrently to the HPV DNA PCR assay. HPV DNA PCR typing was performed using the PCRYrestriction fragment length polymorphism assay; the method and primers are described by Ralston Howe et al.14 Briefly, a fragment of HPV DNA was amplified with a pair of consensus primers. Specimens with positive product were subject to 3 restriction enzymes (Pstl, Rsal, and Haelll) digestion. The digested PCR products were separated on polyacrylamide gels
Volume 41, Number 8, August 2014
511
Copyright © 2014 by the American Sexually Transmitted Diseases Association. Unauthorized reproduction of this article is prohibited.
Brogly et al.
abnormalities only. Statistical analyses were performed using SAS version 9.3 and Stata 11.0.
with a 600-base-pair DNA size standard. A digital image of the subsequent restriction fragment length polymorphism pattern was examined visually for HPV subtypes using the Access Genetics reference database. Vaccine doses received before the study visit were classified into 2 ways in our statistical models: (1) any vaccination (at least 1 vaccine dose) versus unvaccinated and (2) 1 or 2 vaccine doses versus unvaccinated and complete vaccination versus unvaccinated. Differences in the characteristics of women by vaccination were assessed with the W2 and Kruskal-Wallis tests. Abnormal cervical cytology result was classified as atypical cells of undetermined significance (ASCUS), low-grade squamous intraepithelial lesions (LSIL), or high-grade squamous intraepithelial lesions (HSIL). HPV genotypes were classified as (1) any HPV type, (2) HPV vaccine types (6, 11, 16, 18), and (3) high-risk HPV types (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, 68). Prevalence ratios and 95% confidence intervals (CIs) between HPV vaccination and (1) abnormal cervical cytology result and (2) HPV genotype were estimated.15 Unadjusted prevalence ratios were first estimated and then were adjusted for potential confounding from participant age, race, smoking status, age at first sexual intercourse, lifetime number of male sexual partners, condom use, and history of an abnormal cervical cytology result. Minimal confounding was identified, and given the small sample size, models were adjusted for history of cervical
RESULTS A total of 252 women agreed to participate in this study, 235 of whom were confirmed eligible and had a Pap test. These 235 women had a mean age of 26 years, almost 50% had five or more lifetime sexual partners, 50% of those with prior Pap test results had a history of an abnormal cervical cytology result, 18% had received 1 or 2 vaccine doses, and 23% had completed vaccination (Table 1). The mean age at the first vaccine dose was 22 years, and most women initiated vaccination after becoming sexually active. Women older than 25 years who were current or former smokers or had no prior Pap test in their medical records were less likely to be vaccinated. Twenty-four (10%) of the 235 women had an abnormal Pap test result at the study visit including ASCUS (n = 10; 4%), LSIL (n = 12; 5%), and HSIL (n = 2; 1%); 1 woman had an unsatisfactory specimen for evaluation. Among women with an abnormal cervical cytology result, 14 had a prior Pap test at the study clinic, 8 of whom had an abnormal Pap result documented a mean of 10.1 months (range, 5.4Y20.2 months) before the study visit. The adjusted prevalence ratio of abnormal cervical cytology (ASCUS, LSIL, or HSIL) was 65% lower (prevalence ratio, 0.35; 95% CI, 0.14Y0.89; Table 2) in women who received
TABLE 1. Characteristics of the 235 Women in the Study Population by HPV Vaccination Receipt Before the Study Visit (N and Percent or Mean and Range) Characteristic Age, y 21Y25 925Y30 Race Black non-Hispanic White non-Hispanic Hispanic Other or unknown Age at first vaccine dose, y First vaccine dose before sexual activity Yes No Age at first sexual intercourse, y No. lifetime male sexual partners 1 2Y4 5Y9 Q10 or more Unknown Condom use with lifetime male sexual partners Never Sometimes Most of the time Always Unknown Pap test history Normal ASCUS LSIL HSIL No Pap test history in medical record Smoking status Never Former Current
No HPV Vaccination (n = 139)
1Y3 HPV Vaccine Doses (n = 96)
P* 0.06
44 (51.2) 95 (63.8)
42 (48.8) 54 (36.2) 0.20
65 (65.0) 47 (58.8) 14 (56.0) 13 (43.3) V
35 (35.0) 33 (41.3) 11 (44.0) 17 (56.7) 22.2 (16.9Y27.6)
V 16.9 (11Y25)
6 (6.2) 90 (93.8) 17.3 (13Y27)
9 (64.3) 46 (52.9) 43 (60.6) 28 (68.3) 13 (59.1)
5 (35.7) 41 (47.1) 28 (39.4) 13 (31.7) 9 (40.9)
12 (48.0) 36 (56.3) 61 (62.9) 28 (16.9) 2 (66.7)
13 (52.0) 28 (43.8) 36 (37.1) 18 (39.1) 1 (33.3)
35 (56.5) 10 (52.6) 19 (50.0) 1 (20.0) 74 (66.7)
27 (43.6) 9 (47.4) 19 (50.0) 4 (80.0) 37 (33.3)
84 (53.5) 13 (68.4) 42 (71.2)
73 (46.5) 6 (31.6) 17 (28.8)
V V 0.17 0.55
0.70
0.11
0.04
*W2 Test for categorical variables and Kruskal-Wallis test for continuous variables. Age at first vaccination unavailable for 4 women and age at first sexual intercourse unavailable for 1 vaccinated woman.
512
Sexually Transmitted Diseases
&
Volume 41, Number 8, August 2014
Copyright © 2014 by the American Sexually Transmitted Diseases Association. Unauthorized reproduction of this article is prohibited.
HPV Vaccination and Cervical Cytology
TABLE 2.
Prevalence Ratios of Abnormal Cervical Cytology According to HPV Vaccination (n = 234 Women)
HPV Vaccination
Abnormal Cervical Cytology, n (%)
Unadjusted Prevalence Ratio
Adjusted Prevalence Ratio*
None (n = 138) Any (n = 96) None (n = 138) 1Y2 vaccine doses Completed vaccine
19 (13.8) 5 (5.2) 19 (13.8) 3 (7.1) 2 (3.7)
1.0 0.38 (0.15Y0.98) 1.0 0. 52 (0.16Y1.67) 0.27 (0.06Y1.12)
1.0 0.35 (0.14Y0.89) 1.0 0.45 (0.14Y1.44) 0.26 (0.06Y1.07)
*Adjusted for history of abnormal cervical cytology.
any HPV vaccine doses before the study visit versus unvaccinated women. A greater reduction in abnormal cytology results was observed with complete vaccination. Among 232 women with HPV genotyping results, 46 (20%; 95% CI, 15%Y26%) had HPV infection detected, 9 of whom were infected with 2 HPV types. The HPV types detected are shown in Figure 1. The most prevalent HPV types were 16, 18, 45, 53, and 66. Human papillomavirus types could not be identified for 8 women with a single HPV type, and 1 of the 2 types could not be identified in 3 women with 2 HPV types. As expected, women with HPV infection were more likely to have ASCUS, LSIL, or HSIL than women without HPV infection (33% vs. 5%; data not shown). No associations between vaccination and HPV genotype were found, but there was limited power given our small sample size and number of HPV infections (Table 3).
DISCUSSION Although the efficacy of complete HPV vaccination in HPV naBve populations is well documented, the efficacy of incomplete dosing and of vaccination after sexual debut remains unclear.16 In our study, less than half of women received at least
1 HPV vaccine dose, many of whom were incompletely vaccinated. Despite this low rate of vaccination and nearly all women being vaccinated after sexual debut, we found a lower prevalence of abnormal cytology results among vaccinated women. There also was a suggestion of greater protection in women who completed the vaccine, but results were limited by the small number of abnormal cytology results. Our findings are consistent with a recent study that observed decreases in high-grade cervical dysplasia among 21- to 24-year-old women in Connecticut despite low rates of complete vaccination.17 Continued surveillance of vaccination programs is necessary to monitor their success. Women younger than 30 years are the most relevant group for detecting an early impact of HPV vaccination on HPV prevalence.18 The overall prevalence of HPV infection in our study population was slightly lower than that of an American population of unvaccinated minority women whose age range extended beyond that of our population.18 The most prevalent HPV types in our population were 16, 18, 45, 53, and 66, and our prevalence of HPV-16 was lower than that in another study.18 A study of minority 13- to 26-year-olds documented a 15% increase in non-HPV vaccine types after vaccine
Figure 1. HPV genotypes detected by HPV vaccination (n = 232 women)*. Sexually Transmitted Diseases
&
Volume 41, Number 8, August 2014
513
Copyright © 2014 by the American Sexually Transmitted Diseases Association. Unauthorized reproduction of this article is prohibited.
Brogly et al.
TABLE 3.
Prevalence Ratios of HPV Infection According to HPV Vaccination (n = 232 Women)
Infection With Any HPV Type HPV Vaccination
Infection With Any High-Risk HPV Type
HPV Unadjusted Adjusted HPV Unadjusted Adjusted Infection, n (%) Prevalence Ratio Prevalence Ratio* Infection, n (%) Prevalence Ratio Prevalence Ratio*
None (n = 136) Any (n = 96) None (n = 136) 1Y2 vaccine doses (n = 42) Completed vaccine (n = 54)
29 17 29 10 7
(21.3) (17.7) (21.3) (23.8) (13.0)
1.0 0.83 (0.48Y1.42) 1.0 1.12 (0.59Y2.10) 0.61 (0.28Y1.30)
1.0 0.78 (0.46Y1.33) 1.0 1.01 (0.55Y1.86) 0.59 (0.28Y1.25)
17 (12.2) 10 (10.4) 17 (12.2) 5 (11.9) 5 (9.3)
1.0 0.83 (0.40Y1.74) 1.0 0.95 (0.38Y2.43) 0.74 (0.29Y1.91)
1.0 0.72 (0.35Y1.46) 1.0 0.76 (0.31Y1.86) 0.69 (0.28Y1.70)
*Adjusted for history of abnormal cervical cytology.
implementation.19 Our study had too few HPV infections to statistically examine differences in nonvaccine types by vaccination. Furthermore, we were unable to examine associations between vaccination and HPV-16 and HPV-18. Some limitations of our study are the cross-sectional design, which includes both incident and prevalent cervical dysplasia and HPV infection. We were, however, able to classify vaccination temporally with respect to the study visit and Pap test. Only 1 vaccinated woman with a prevalent cervical abnormality initiated vaccination after identification of cervical dysplasia, and results were unchanged when this woman was excluded from our analyses. Another limitation of our study is that HPV vaccination was implemented in 2007 at the study clinic, and therefore, very few women vaccinated before sexual debut were included in the study population. Finally, our HPV genotypes were based on Pap test specimens obtained for clinical care, and some genotypes could not be determined. We attribute this to infection with uncommon HPV types that were unavailable in the subtyping reference database. Human papillomavirus vaccination rates remain low in the United States,6 with the lowest rates reported among 18- to 26-year-old women. Although data clearly indicate better immune responses and vaccine efficacy against both genital warts and cervical dysplasia when vaccination occurs before age 17 years,20 this cross-sectional study suggests that HPV vaccination may be effective in reducing abnormal Pap test results after sexual debut, as has been observed in other studies.17 Studies should continue to compare vaccine effectiveness before and after sexual debut and by vaccine doses received, and to explore the role of herd immunity. REFERENCES 1. Future II Study Group. Quadrivalent vaccine against human papillomavirus to prevent high-grade cervical lesions. N Engl J Med 2007; 356:1915Y1927. 2. Paavonen J, Jenkins D, Bosch F, et al. Efficacy of a prophylactic adjuvanted bivalent L1 virus-like-particle vaccine against infection with human papillomavirus types 16 and 18 in young women: An interim analysis of a phase III double-blind, randomised controlled trial. Lancet 2007; 369:2161Y2170. 3. Centers for Disease Control and Prevention. FDA licensure of bivalent human papillomavirus vaccine (HPV2, Cervarix) for use in females and updated HPV vaccination recommendations from the Advisory Committee on Immunization Practices (ACIP). MMWR Morb Mortal Wkly Rep 2010; 59:626Y629. 4. Laz TH, Rahman M, Berenson AB. An update on human papillomavirus vaccine uptake among 11Y17 year old girls in the United States: National Health Interview Survey, 2010. Vaccine 2012; 30:3534Y3540.
514
5. Gefenaite G, Smit M, Nijman HW, et al. Comparatively low attendance during human papillomavirus catch-up vaccination among teenage girls in the Netherlands: Insights from a behavioral survey among parents. BMC Public Health 2012; 12:498Y506. 6. Centers for Disease Control and Prevention. National and state vaccination coverage among adolescents aged 13Y17 yearsVUnited States, 2012. MMWR Morb Mortal Wkly Rep 2013; 62:685Y693. 7. Dorell CG, Yankey D, Santibanez TA, et al. Human papillomavirus vaccination series initiation and completion, 2008Y2009. Pediatrics 2011; 128:830Y839. 8. Kahn JA, Lan D, Kahn RS. Sociodemographic factors associated with high-risk human papillomavirus infection. Obstet Gynecol 2007; 110:87Y95. 9. Watson M, Saraiya M, Benard V, et al. Burden of cervical cancer in the United States, 1998Y2003. Cancer 2008; 113(10 Suppl): 2855Y2864. 10. Krogstad P, Cherry J. Quadrivalent human vaccineVA call to action and for additional research. Pediatr Res 2007; 62:527. 11. Lynge E, Antilla A, Arbyn M, et al. What’s next? Perspectives and future needs of cervical screening in Europe in the era of molecular testing and vaccination. Eur J Cancer 2009; 45:2714Y2721. 12. Hariri S, Markowitz LE, Dunne EF, et al. Population impact of HPV vaccines: Summary of early evidence. J Adoles Health 2013; 53:679Y682. 13. Perkins RB, Brogly SB, Adams WG, et al. Correlates of human papillomavirus vaccination rates in low-income, minority adolescents: A multicenter study. J Womens Health (Larchmt) 2012; 21:813Y820. 14. Ralston Howe E, Li Z, McGlennen R, et al. Type-specific prevalence and persistence of human papillomavirus in women in the United States who are referred for typing as a component of cervical cancer screening. Am J Obstet Gynecol 2009; 200:e241Ye247. 15. Spiegelman D, Hertzmark E. Easy SAS calculations for risk or prevalence ratios and differences. Am J Epidemiol 2005; 162:199Y200. 16. Szarewski A. HPV vaccination and cervical cancer. Curr Oncol Rep 2012; 14:559Y567. 17. Niccolai LM, Julian PJ, Meek JI, et al. Declining rates of high-grade cervical lesions in young women in Connecticut, 2008Y2011. Cancer Epidemiol Biomarkers Prev 2013; 22:1446Y1450. 18. Wheeler CM, Hunt WC, Cuzick J, et al. A population-based study of human papillomavirus genotype prevalence in the United States: Baseline measures prior to mass human papillomavirus vaccination. Int J Cancer 2012; 132:198Y207. 19. Kahn JA, Brown DR, Ding L, et al. Vaccine-type human papillomavirus and evidence of herd protection after vaccine introduction. Pediatrics 2012; 130:e249Ye256. 20. Markowitz LE, Hariri S, Lin C, et al. Reduction in human papillomavirus (HPV) prevalence among young women following HPV vaccine introduction in the United States, National Health and Nutrition Examination Surveys, 2003Y2010. J Infect Dis 2013; 208:385Y393.
Sexually Transmitted Diseases
&
Volume 41, Number 8, August 2014
Copyright © 2014 by the American Sexually Transmitted Diseases Association. Unauthorized reproduction of this article is prohibited.
Human Papillomavirus Vaccination and Cervical Cytology in Young Minority Women Susan B. Brogly, PhD, MSc,* Rebecca B. Perkins, MD, MSc,Þ Dimity Zepf, BS,þ Janina Longtine, MD,§ and Shi Yang, MD, MSc¶ Background: Continued surveillance of human papillomavirus (HPV) vaccination is necessary to identify clinical benefits, particularly given the low rate of vaccine uptake and completion and vaccination of many young women after sexual debut. We studied the effect of catch-up HPV vaccination on cervical cytology and HPV infection in sexually active, low-income and minority young women. Methods: We conducted a cross-sectional study of 235 women aged 21 to 30 years undergoing routine cervical cytology testing. Demographic and behavioral characteristics were self-reported. HPV vaccination status was determined by self-report and verified with electronic medical records. Liquid-based cytology samples were tested for HPV genotypes. Adjusted prevalence ratios between HPV vaccination and (1) abnormal cervical cytology result and (2) HPV genotype were estimated. Findings: At the time of the study, 96 women (41%) had received at least 1 HPV vaccination, 54 of whom had completed the series; 97% of women were vaccinated after sexual debut. Twenty-four (10%) women had an abnormal cervical cytology result. The prevalence of abnormal cytology was 65% lower in women who received at least 1 HPV vaccination versus unvaccinated women (adjusted prevalence ratio, 0.35; 95% confidence interval, 0.14Y0.89). Among 232 women with genotype results, 46 (20%; 95% confidence interval, 15%Y26%) had HPV infection detected. HPV types 16, 18, 45, 53, and 66 were most prevalent. Conclusions: The prevalence of abnormal cytology was lower in vaccinated versus unvaccinated women, despite receipt of vaccination after sexual debut. Continued assessment of HPV vaccine effectiveness before and after sexual debut on HPV infection and cervical dysplasia is needed.
T
he human papillomavirus (HPV) vaccine demonstrated high efficacy in preventing HPV infection and disease in women aged 16 to 26 years, with the highest efficacy against HPV types 16 and 18 in women without prior HPV infection.1,2 In the United States, routine vaccination with the quadrivalent HPV vaccine (HPV types 6, 11, 16, 18) is recommended for girls 11 to 12 years of age, and catch-up vaccination is recommended
From the *Department of Epidemiology, Boston University School of Public Health, Boston, MA; †Department of Obstetrics and Gynecology, Boston University School of Medicine, Boston, MA; ‡Department of Pathology, Brigham and Women’s Hospital, Boston, MA; §Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY; and ¶Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, MA
The authors thank the women for participating in this study. The authors are grateful to Sonya Kovacic and Dr Myrlene Jeudy for their assistance with patient recruitment and data collection. The authors thank Ron McGlennen at Access Genetics for subtyping software access. This study was funded by the American Cancer Society, ACS Grant IRG-72-001-35-IRG. Conflict of interest: None declared. Correspondence: Susan Brogly, PhD, MSc, Department of Epidemiology, Boston University School of Public Health, 715 Albany St, Talbot 419E, Boston, MA 02118. E-mail: [email protected]. Received for publication March 6, 2014, and accepted June 13, 2014. DOI: 10.1097/OLQ.0000000000000162 Copyright * 2014 American Sexually Transmitted Diseases Association All rights reserved.
Sexually Transmitted Diseases
&
for girls and women 13 through 26 years of age.3 Vaccine uptake and completion, however, has been low.4,5 In 2012, 54% of young girls initiated vaccination and 33% completed vaccination.6 The observed incomplete vaccination of low-income and minority women in the Unites States7 is particularly concerning because of the high rates of HPV infection and cervical cancer in these women.8,9 Additional surveillance of vaccine effectiveness of these women is needed.10Y12 We conducted a cross-sectional study of HPV vaccination and (1) cervical cytology and (2) HPV infection among lowincome, minority young women attending a large volume safety-net hospital clinic. We previously reported low vaccine uptake and completion in adolescents of this population.13
METHODS This study was conducted in an obstetrics and gynecology clinic of a safety-net hospital serving a low-income, minority population of inner-city Boston. Women 21 to 30 years of age who presented to the study clinic for a scheduled Papanicolaou (Pap) test from April 2011 to March 2012 were eligible for participation. Our selected age range for study participation was based on clinical care: (1) the HPV vaccine was implemented in 2007 for women 11 to 26 years of age, and thus, at the time of study enrollment, all participants had been eligible for vaccination in 2007 to 2011, and (2) because leftover clinical Pap test specimens were used in our study for HPV genotyping, we restricted the study to women 21 years or older who undergo routine Pap tests. All study participants signed an informed consent form in English or Spanish. Participants completed a short questionnaire on smoking status, HPV vaccination, age of first sexual intercourse, lifetime number of male sexual partners, and usual condom use with these male partners. Electronic medical records were used to supplement information on these variables and to obtain information on prior Pap test results. Participants received a US $5 pharmacy gift certificate as compensation for their time. This study was approved by the research review board of Boston University Medical Center. Cytology specimens were collected per routine clinical practice by using the Thinprep system; cytopathology slides were prepared for Pap test staining. The remaining collections were resuspended in 2 mL of buffer and used for HPV genotyping with the technician blinded to the Pap test result. DNA extraction was performed using the QIAgen QIAamp DNA Kit. The sample was centrifuged to a pellet cellular material, and the pellet was digested overnight with ATL (tissue lysis buffer) and proteinase K. DNA quality was assayed by polymerase chain reaction (PCR) amplification of A-globin (500-base-pair product) concurrently to the HPV DNA PCR assay. HPV DNA PCR typing was performed using the PCRYrestriction fragment length polymorphism assay; the method and primers are described by Ralston Howe et al.14 Briefly, a fragment of HPV DNA was amplified with a pair of consensus primers. Specimens with positive product were subject to 3 restriction enzymes (Pstl, Rsal, and Haelll) digestion. The digested PCR products were separated on polyacrylamide gels
Volume 41, Number 8, August 2014
511
Copyright © 2014 by the American Sexually Transmitted Diseases Association. Unauthorized reproduction of this article is prohibited.
Brogly et al.
abnormalities only. Statistical analyses were performed using SAS version 9.3 and Stata 11.0.
with a 600-base-pair DNA size standard. A digital image of the subsequent restriction fragment length polymorphism pattern was examined visually for HPV subtypes using the Access Genetics reference database. Vaccine doses received before the study visit were classified into 2 ways in our statistical models: (1) any vaccination (at least 1 vaccine dose) versus unvaccinated and (2) 1 or 2 vaccine doses versus unvaccinated and complete vaccination versus unvaccinated. Differences in the characteristics of women by vaccination were assessed with the W2 and Kruskal-Wallis tests. Abnormal cervical cytology result was classified as atypical cells of undetermined significance (ASCUS), low-grade squamous intraepithelial lesions (LSIL), or high-grade squamous intraepithelial lesions (HSIL). HPV genotypes were classified as (1) any HPV type, (2) HPV vaccine types (6, 11, 16, 18), and (3) high-risk HPV types (16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, 68). Prevalence ratios and 95% confidence intervals (CIs) between HPV vaccination and (1) abnormal cervical cytology result and (2) HPV genotype were estimated.15 Unadjusted prevalence ratios were first estimated and then were adjusted for potential confounding from participant age, race, smoking status, age at first sexual intercourse, lifetime number of male sexual partners, condom use, and history of an abnormal cervical cytology result. Minimal confounding was identified, and given the small sample size, models were adjusted for history of cervical
RESULTS A total of 252 women agreed to participate in this study, 235 of whom were confirmed eligible and had a Pap test. These 235 women had a mean age of 26 years, almost 50% had five or more lifetime sexual partners, 50% of those with prior Pap test results had a history of an abnormal cervical cytology result, 18% had received 1 or 2 vaccine doses, and 23% had completed vaccination (Table 1). The mean age at the first vaccine dose was 22 years, and most women initiated vaccination after becoming sexually active. Women older than 25 years who were current or former smokers or had no prior Pap test in their medical records were less likely to be vaccinated. Twenty-four (10%) of the 235 women had an abnormal Pap test result at the study visit including ASCUS (n = 10; 4%), LSIL (n = 12; 5%), and HSIL (n = 2; 1%); 1 woman had an unsatisfactory specimen for evaluation. Among women with an abnormal cervical cytology result, 14 had a prior Pap test at the study clinic, 8 of whom had an abnormal Pap result documented a mean of 10.1 months (range, 5.4Y20.2 months) before the study visit. The adjusted prevalence ratio of abnormal cervical cytology (ASCUS, LSIL, or HSIL) was 65% lower (prevalence ratio, 0.35; 95% CI, 0.14Y0.89; Table 2) in women who received
TABLE 1. Characteristics of the 235 Women in the Study Population by HPV Vaccination Receipt Before the Study Visit (N and Percent or Mean and Range) Characteristic Age, y 21Y25 925Y30 Race Black non-Hispanic White non-Hispanic Hispanic Other or unknown Age at first vaccine dose, y First vaccine dose before sexual activity Yes No Age at first sexual intercourse, y No. lifetime male sexual partners 1 2Y4 5Y9 Q10 or more Unknown Condom use with lifetime male sexual partners Never Sometimes Most of the time Always Unknown Pap test history Normal ASCUS LSIL HSIL No Pap test history in medical record Smoking status Never Former Current
No HPV Vaccination (n = 139)
1Y3 HPV Vaccine Doses (n = 96)
P* 0.06
44 (51.2) 95 (63.8)
42 (48.8) 54 (36.2) 0.20
65 (65.0) 47 (58.8) 14 (56.0) 13 (43.3) V
35 (35.0) 33 (41.3) 11 (44.0) 17 (56.7) 22.2 (16.9Y27.6)
V 16.9 (11Y25)
6 (6.2) 90 (93.8) 17.3 (13Y27)
9 (64.3) 46 (52.9) 43 (60.6) 28 (68.3) 13 (59.1)
5 (35.7) 41 (47.1) 28 (39.4) 13 (31.7) 9 (40.9)
12 (48.0) 36 (56.3) 61 (62.9) 28 (16.9) 2 (66.7)
13 (52.0) 28 (43.8) 36 (37.1) 18 (39.1) 1 (33.3)
35 (56.5) 10 (52.6) 19 (50.0) 1 (20.0) 74 (66.7)
27 (43.6) 9 (47.4) 19 (50.0) 4 (80.0) 37 (33.3)
84 (53.5) 13 (68.4) 42 (71.2)
73 (46.5) 6 (31.6) 17 (28.8)
V V 0.17 0.55
0.70
0.11
0.04
*W2 Test for categorical variables and Kruskal-Wallis test for continuous variables. Age at first vaccination unavailable for 4 women and age at first sexual intercourse unavailable for 1 vaccinated woman.
512
Sexually Transmitted Diseases
&
Volume 41, Number 8, August 2014
Copyright © 2014 by the American Sexually Transmitted Diseases Association. Unauthorized reproduction of this article is prohibited.
HPV Vaccination and Cervical Cytology
TABLE 2.
Prevalence Ratios of Abnormal Cervical Cytology According to HPV Vaccination (n = 234 Women)
HPV Vaccination
Abnormal Cervical Cytology, n (%)
Unadjusted Prevalence Ratio
Adjusted Prevalence Ratio*
None (n = 138) Any (n = 96) None (n = 138) 1Y2 vaccine doses Completed vaccine
19 (13.8) 5 (5.2) 19 (13.8) 3 (7.1) 2 (3.7)
1.0 0.38 (0.15Y0.98) 1.0 0. 52 (0.16Y1.67) 0.27 (0.06Y1.12)
1.0 0.35 (0.14Y0.89) 1.0 0.45 (0.14Y1.44) 0.26 (0.06Y1.07)
*Adjusted for history of abnormal cervical cytology.
any HPV vaccine doses before the study visit versus unvaccinated women. A greater reduction in abnormal cytology results was observed with complete vaccination. Among 232 women with HPV genotyping results, 46 (20%; 95% CI, 15%Y26%) had HPV infection detected, 9 of whom were infected with 2 HPV types. The HPV types detected are shown in Figure 1. The most prevalent HPV types were 16, 18, 45, 53, and 66. Human papillomavirus types could not be identified for 8 women with a single HPV type, and 1 of the 2 types could not be identified in 3 women with 2 HPV types. As expected, women with HPV infection were more likely to have ASCUS, LSIL, or HSIL than women without HPV infection (33% vs. 5%; data not shown). No associations between vaccination and HPV genotype were found, but there was limited power given our small sample size and number of HPV infections (Table 3).
DISCUSSION Although the efficacy of complete HPV vaccination in HPV naBve populations is well documented, the efficacy of incomplete dosing and of vaccination after sexual debut remains unclear.16 In our study, less than half of women received at least
1 HPV vaccine dose, many of whom were incompletely vaccinated. Despite this low rate of vaccination and nearly all women being vaccinated after sexual debut, we found a lower prevalence of abnormal cytology results among vaccinated women. There also was a suggestion of greater protection in women who completed the vaccine, but results were limited by the small number of abnormal cytology results. Our findings are consistent with a recent study that observed decreases in high-grade cervical dysplasia among 21- to 24-year-old women in Connecticut despite low rates of complete vaccination.17 Continued surveillance of vaccination programs is necessary to monitor their success. Women younger than 30 years are the most relevant group for detecting an early impact of HPV vaccination on HPV prevalence.18 The overall prevalence of HPV infection in our study population was slightly lower than that of an American population of unvaccinated minority women whose age range extended beyond that of our population.18 The most prevalent HPV types in our population were 16, 18, 45, 53, and 66, and our prevalence of HPV-16 was lower than that in another study.18 A study of minority 13- to 26-year-olds documented a 15% increase in non-HPV vaccine types after vaccine
Figure 1. HPV genotypes detected by HPV vaccination (n = 232 women)*. Sexually Transmitted Diseases
&
Volume 41, Number 8, August 2014
513
Copyright © 2014 by the American Sexually Transmitted Diseases Association. Unauthorized reproduction of this article is prohibited.
Brogly et al.
TABLE 3.
Prevalence Ratios of HPV Infection According to HPV Vaccination (n = 232 Women)
Infection With Any HPV Type HPV Vaccination
Infection With Any High-Risk HPV Type
HPV Unadjusted Adjusted HPV Unadjusted Adjusted Infection, n (%) Prevalence Ratio Prevalence Ratio* Infection, n (%) Prevalence Ratio Prevalence Ratio*
None (n = 136) Any (n = 96) None (n = 136) 1Y2 vaccine doses (n = 42) Completed vaccine (n = 54)
29 17 29 10 7
(21.3) (17.7) (21.3) (23.8) (13.0)
1.0 0.83 (0.48Y1.42) 1.0 1.12 (0.59Y2.10) 0.61 (0.28Y1.30)
1.0 0.78 (0.46Y1.33) 1.0 1.01 (0.55Y1.86) 0.59 (0.28Y1.25)
17 (12.2) 10 (10.4) 17 (12.2) 5 (11.9) 5 (9.3)
1.0 0.83 (0.40Y1.74) 1.0 0.95 (0.38Y2.43) 0.74 (0.29Y1.91)
1.0 0.72 (0.35Y1.46) 1.0 0.76 (0.31Y1.86) 0.69 (0.28Y1.70)
*Adjusted for history of abnormal cervical cytology.
implementation.19 Our study had too few HPV infections to statistically examine differences in nonvaccine types by vaccination. Furthermore, we were unable to examine associations between vaccination and HPV-16 and HPV-18. Some limitations of our study are the cross-sectional design, which includes both incident and prevalent cervical dysplasia and HPV infection. We were, however, able to classify vaccination temporally with respect to the study visit and Pap test. Only 1 vaccinated woman with a prevalent cervical abnormality initiated vaccination after identification of cervical dysplasia, and results were unchanged when this woman was excluded from our analyses. Another limitation of our study is that HPV vaccination was implemented in 2007 at the study clinic, and therefore, very few women vaccinated before sexual debut were included in the study population. Finally, our HPV genotypes were based on Pap test specimens obtained for clinical care, and some genotypes could not be determined. We attribute this to infection with uncommon HPV types that were unavailable in the subtyping reference database. Human papillomavirus vaccination rates remain low in the United States,6 with the lowest rates reported among 18- to 26-year-old women. Although data clearly indicate better immune responses and vaccine efficacy against both genital warts and cervical dysplasia when vaccination occurs before age 17 years,20 this cross-sectional study suggests that HPV vaccination may be effective in reducing abnormal Pap test results after sexual debut, as has been observed in other studies.17 Studies should continue to compare vaccine effectiveness before and after sexual debut and by vaccine doses received, and to explore the role of herd immunity. REFERENCES 1. Future II Study Group. Quadrivalent vaccine against human papillomavirus to prevent high-grade cervical lesions. N Engl J Med 2007; 356:1915Y1927. 2. Paavonen J, Jenkins D, Bosch F, et al. Efficacy of a prophylactic adjuvanted bivalent L1 virus-like-particle vaccine against infection with human papillomavirus types 16 and 18 in young women: An interim analysis of a phase III double-blind, randomised controlled trial. Lancet 2007; 369:2161Y2170. 3. Centers for Disease Control and Prevention. FDA licensure of bivalent human papillomavirus vaccine (HPV2, Cervarix) for use in females and updated HPV vaccination recommendations from the Advisory Committee on Immunization Practices (ACIP). MMWR Morb Mortal Wkly Rep 2010; 59:626Y629. 4. Laz TH, Rahman M, Berenson AB. An update on human papillomavirus vaccine uptake among 11Y17 year old girls in the United States: National Health Interview Survey, 2010. Vaccine 2012; 30:3534Y3540.
514
5. Gefenaite G, Smit M, Nijman HW, et al. Comparatively low attendance during human papillomavirus catch-up vaccination among teenage girls in the Netherlands: Insights from a behavioral survey among parents. BMC Public Health 2012; 12:498Y506. 6. Centers for Disease Control and Prevention. National and state vaccination coverage among adolescents aged 13Y17 yearsVUnited States, 2012. MMWR Morb Mortal Wkly Rep 2013; 62:685Y693. 7. Dorell CG, Yankey D, Santibanez TA, et al. Human papillomavirus vaccination series initiation and completion, 2008Y2009. Pediatrics 2011; 128:830Y839. 8. Kahn JA, Lan D, Kahn RS. Sociodemographic factors associated with high-risk human papillomavirus infection. Obstet Gynecol 2007; 110:87Y95. 9. Watson M, Saraiya M, Benard V, et al. Burden of cervical cancer in the United States, 1998Y2003. Cancer 2008; 113(10 Suppl): 2855Y2864. 10. Krogstad P, Cherry J. Quadrivalent human vaccineVA call to action and for additional research. Pediatr Res 2007; 62:527. 11. Lynge E, Antilla A, Arbyn M, et al. What’s next? Perspectives and future needs of cervical screening in Europe in the era of molecular testing and vaccination. Eur J Cancer 2009; 45:2714Y2721. 12. Hariri S, Markowitz LE, Dunne EF, et al. Population impact of HPV vaccines: Summary of early evidence. J Adoles Health 2013; 53:679Y682. 13. Perkins RB, Brogly SB, Adams WG, et al. Correlates of human papillomavirus vaccination rates in low-income, minority adolescents: A multicenter study. J Womens Health (Larchmt) 2012; 21:813Y820. 14. Ralston Howe E, Li Z, McGlennen R, et al. Type-specific prevalence and persistence of human papillomavirus in women in the United States who are referred for typing as a component of cervical cancer screening. Am J Obstet Gynecol 2009; 200:e241Ye247. 15. Spiegelman D, Hertzmark E. Easy SAS calculations for risk or prevalence ratios and differences. Am J Epidemiol 2005; 162:199Y200. 16. Szarewski A. HPV vaccination and cervical cancer. Curr Oncol Rep 2012; 14:559Y567. 17. Niccolai LM, Julian PJ, Meek JI, et al. Declining rates of high-grade cervical lesions in young women in Connecticut, 2008Y2011. Cancer Epidemiol Biomarkers Prev 2013; 22:1446Y1450. 18. Wheeler CM, Hunt WC, Cuzick J, et al. A population-based study of human papillomavirus genotype prevalence in the United States: Baseline measures prior to mass human papillomavirus vaccination. Int J Cancer 2012; 132:198Y207. 19. Kahn JA, Brown DR, Ding L, et al. Vaccine-type human papillomavirus and evidence of herd protection after vaccine introduction. Pediatrics 2012; 130:e249Ye256. 20. Markowitz LE, Hariri S, Lin C, et al. Reduction in human papillomavirus (HPV) prevalence among young women following HPV vaccine introduction in the United States, National Health and Nutrition Examination Surveys, 2003Y2010. J Infect Dis 2013; 208:385Y393.
Sexually Transmitted Diseases
&
Volume 41, Number 8, August 2014
Copyright © 2014 by the American Sexually Transmitted Diseases Association. Unauthorized reproduction of this article is prohibited.
