Multiple-type human papillomavirus infection in younger uncircumcised men

Abstract

A cohort of 388 young men enrolled for military service in the Danish army was established and the participants underwent a clinical examination with human papillomavirus (HPV) testing. In addition, a questionnaire containing questions regarding sociodemographic variables, sexual habits and lifestyle factors was completed. The prevalence of HPV was 33.4% in this cohort of uncircumcised men aged 18–29 years. Multiple HPV types were prevalent with one-third of the HPV-positive men being positive for more than one HPV type. Number of recent sexual partners and infrequent condom use were strong risk factors, particularly in men having multiple HPV types. Our findings re-emphasize the importance of sexual transmission and also point to a role of factors that may be related to individual susceptibility as genital warts, alcohol intake and, to a lesser extent, smoking were strongly associated with having multiple HPV types.

Keywords

human papillomavirus HPV sexually transmitted infection HPV DNA testing risk factors prevalence men genital warts multiple-type HPV infection

Introduction

The concept of the ‘male factor’ in cervical carcinogenesis is widely accepted, i.e. women with male partners having had multiple sexual partners are at increased risk for cervical human papillomavirus (HPV) infection and cervical intraepithelial neoplasia.¹ Thus, it is important to gain an insight into the nature of genital HPV infection in men.

Factors suggested to be associated with genital HPV infection in men include among others non-circumcision,^2,3 previous sexually transmitted infections (STIs)⁴ and increasing lifetime number of sexual partners,^3,5,6 the latter also being the major risk factor for HPV infection in women. An earlier study on Finnish conscripts showed that reporting more casual sexual partners and more previous STIs were associated with genital HPV infection.⁷ Multiple-type HPV infection in women has been associated with younger age, increased risk of persistence and more severe cervical lesions.^1,8,9 Information about the prevalence of and risk factors for multiple-type HPV infection in men is still relatively limited. However, two studies have reported an increased risk for persistence in men with multiple HPV types at enrolment.^10,11 Consequently, the current findings may indicate that the presence of multiple HPV types increases the risk for HPV-related cancer in both women and men.

In the present cross-sectional study we assessed the prevalence of genital HPV infection in a cohort of young, uncircumcised Danish men with particular focus on the occurrence of multiple HPV types and the type-distribution in relation to the currently available HPV vaccines. Furthermore, we wanted to identify potential risk factors for multiple-type and single-type prevalent HPV infection.

Materials and Methods

Data collection

A cohort of young men, who were enrolled for military service in the Danish Army, was established. In Denmark, military service is mandatory for men. Details of the enrolment procedure and data collection have been provided previously.¹¹ In brief, new conscripts (n = 752) at Hoevelte and Sjaelsmark barracks (greater Copenhagen area) due to start of their military service were potentially eligible for the study and were invited to participate. On the examination days, 636 men were eligible, and 116 men were ineligible for a variety of reasons, e.g. being on leave or participating in military exercises. We included 388 volunteers (61%) who all signed an informed-consent form, and were paid approximately US$20 for the inconvenience. The study was approved by the Scientific Ethics Committee for Copenhagen and Frederiksberg Municipality and by the Danish Data Protection Board.

Initially, a clinical examination with regard to circumcision status and presence of genital warts was performed. The HPV analyses were based on cellular material obtained from glans penis and coronal sulcus using pre-moistened cotton-tipped, plastic-shafted swabs. In our hands, this method has yielded the highest amount of cells and the lowest occurrence of β-globin-negative samples. In the present analyses, we only use results from the samples obtained from the glans/coronal sulcus, yielding a study population of 350 soldiers with β-globin-positive samples.

By means of a structured self-administered questionnaire information about sociodemographic variables, sexual behaviour, STIs, contraception, smoking and alcohol consumption was obtained. We did not ask about sexual preference, i.e. whether they defined themselves as homosexual or heterosexual. The questionnaires were answered in privacy in special rooms at each of the barracks.

HPV DNA analysis (polymerase chain reaction)

The penile swabs were collected as described above and stored in 3 mL phosphate-buffered saline containing 0.05% methiolate and kept at ~4°C until shipment. The samples were sent to the HPV testing laboratory (Department of Pathology, VU Medical Center, Amsterdam, The Netherlands) on the day of collection. After vortexing vigorously, the suspensions were centrifuged for 10 minutes at 3000 g. The cell pellets were re-suspended in 100 μL 10 mmol/L Tris HCl, pH 7.4 and frozen at –80°C

A detailed description of the HPV DNA analysis was given previously.¹¹ In brief, the detection of a broad spectrum of mucosotropic HPV types was performed by a general primer GP5+/6+ mediated polymerase chain reaction enzyme immunoassay (PCR-EIA) as previously described in detail,¹² except that another PCR processor and programme was used. The general primer polymerase chain reaction (GP-PCR) products were analysed by EIA using two cocktail oligoprobes to identify high-risk HPVs (16,18, 31, 33, 35, 39,45, 51, 52,56, 58, 59, 66 and 68) and low-risk HPVs (6, 11, 26, 34, 40, 42, 43, 44, 53, 54, 55,57, 61, 70, 71, 72, 73, 81 [CP8304], 82 [MM4/IS39], 83 [MM7], 84 [MM8] and 89 [CP6108]). Subsequently, high-risk and low-risk positive samples were subjected to individual typing using EIA and HPV type-specific oligoprobes. Finally, to detect HPV types (named HPVX) which were not identified by high-risk/low-risk EIAs, GP-PCR products were subjected to Southern blot analysis under low stringent conditions with a cocktail probe consisting of GP-PCR products that were specific for HPV6, 11, 16, 18, 31 and 33 as previously described by van den Brule et al.¹³.

HPV26, 34, 53, 73 and 82 were included in the low-risk oligoprobe. However, since types 73 and 82 have been epidemiologically found to belong to the high-risk group they were included in the HPV high-risk group. In the study population only two men had type 73 and none had type 82. Types 26, 34 and 53 remained in the low-risk (LR) group since they are epidemiologically categorized as only probably high-risk (HR) types. Only one participant had type 34 and none had types 26 or 53.

Statistical analysis

The association between different variables and genital HPV infection was examined by computing odds ratio (OR) with a 95% confidence interval (CI). By means of unconditional, multiple logistic regression analysis we assessed the association between outcome and potential determinants with simultaneous adjustment for other risk factors. Selection of variables included in the multivariate model was made among variables that were significant at a 10% level in the age-adjusted model. Subsequently, stepwise regression was performed to define the final multivariate model. In the final model we included those variables found to be significantly associated with the risk of prevalent HPV infection and variables that had an influence on the other variables.

In addition, we made two separate analyses using the two outcomes of HPV single-type infections and HPV multiple-type infections. In both analyses, HPV-negative men constituted the non-case group.

Results

The age range in the study population was 18–29 years with 92% of the men being between 19 and 22 years of age. Most men reported being single (90%), the remainder being cohabiting or married. In all, 66% had 11 or more years at school, 28% had 10 years and 6% had nine years or less. None of the men were circumcised. Nineteen men (5%) had never had sexual intercourse whereas 25% reported 10 or more partners. Thirty percent had had their first sexual intercourse within the last three years and for 30% it was six years ago or more.

HPV prevalence and HPV-type distribution

Table 1 shows the HPV status of the 350 β-globin positive men. In all, 117 men (33.4%; 95% CI: 28.5–38.4) had HPV DNA detected (any type). HR types were present in 54 men (overall prevalence: 15.4%; 95% CI: 11.8–19.6, prevalence among HPV-positive men; 46.2%; 95% CI: 36.9–55.6) whereas LR types were present in 23 men (overall prevalence: 6.6%; 95% CI: 4.2–9.7, prevalence among HPV-positive men; 19.7%; 95% CI: 12.9–28.0). In total, 18 men had both HR and LR types accounting for an overall prevalence of 5.1% (95% CI: 3.1–8.0) and a prevalence among HPV-positive men of 15.4% (95% CI: 9.4–23.2). The remaining 22 men were positive for an undetermined HPV type. Single-type infection was present in 56 men (overall prevalence: 16.0%; 95% CI: 12.2–19.8, prevalence among HPV-positive men; 47.9%; 95% CI: 38.8–56.9). Multiple HPV types were detected in 39 men, accounting for an overall prevalence of 11.1% (95% CI: 7.9–14.4) and a prevalence of 33.3% (95% CI: 24.8–41.9) among HPV-positive men. The type-distribution is shown in Figure 1. Overall, HPV16 was the most common type with a prevalence of 6.6%, followed by HPV56 (4.9%), HPV6 (4.6%) and HPV18 (3.7%).

Table 1

Human papillomavirus status of the β-globin-positive study participants (N = 350)

HPV status	n	Prevalence (95% CI)
Overall
HPV negative	233	66.6 (61.6–71.5)
HPV positive	117	33.4 (28.5–38.4)
HR types	54	15.4 (11.8–19.6)
LR types	23	6.6 (4.2–9.7)
HR and LR types	18	5.1 (3.1–8.0)
Single type	56	16.0 (12.2–19.8)
Multiple types	39	11.1 (7.9–14.4)
Unknown types	22	6.3 (3.7–8.8)
Vaccine types
HPV16 alone	10	2.9 (1.1–4.6)
HPV16 with other HPV types	13	3.7 (1.7–5.7)
HPV18 alone	5	1.4 (0.2–2.7)
HPV18 with other HPV types	8	2.3 (0.7–3.9)
HPV6 alone	7	2.0 (0.5–3.5)
HPV6 with other HPV types	9	2.6 (0.9–4.2)
HPV11 alone	1	0.3 (0.0–0.8)
HPV11 with other HPV types	0	–

HPV, human papillomavirus; HR, high-risk; LR, low-risk

Figure 1

Human papillomavirus-type distribution among 388 Danish conscripts (high-risk HPV types = blue, low-risk HPV types = green)

Regarding the four HPV types in the quadrivalent vaccine, HPV16 was the most prevalent type. HPV16 was detected alone in 10 men (2.9% of the total study population) and in 13 men HPV16 was detected together with other HPV types, accounting for 3.7% of the total study population. HPV18 was detected alone in 1.4% of the study population and together with other HPV types in 2.3% of the men. The corresponding numbers regarding HPV6 were 2.0% alone and 2.6% in multiple infections. HPV11 was only present in one man in the study population (Table 1). In total, 44 men were positive for at least one of the four vaccine types (overall prevalence: 12.6%; 95% CI: 9.1–16.0, prevalence among HPV-positive men; 37.6%; 95% CI: 28.6–46.4) (data not shown). No men were HPV-positive for all four vaccine types (data not shown).

Risk factors for genital HPV infection

In Table 2, the risk factors for prevalent HPV infection are presented. Age was not significantly associated with risk of HPV infection. Men with 10 years or less of schooling had an increased risk of HPV infection compared with men with a higher educational level (OR = 1.86; 95% CI: 1.10–3.12). After adjustment for potential confounders, no statistically significant associations were observed between HPV positivity and smoking and alcohol intake, respectively.

Table 2

Determinants of prevalent human papillomavirus infection among young Danish male conscripts

	Any HPV type
Variables	n (% pos)	OR^†	OR^‡	95% CI
Age (per year)		1.15	1.06	(0.88–1.27)
Years of schooling
≥11	227 (27.3)	1.00	1.00	ref.
≤10	122 (44.3)	2.04^∗	1.86	(1.10–3.12)
Smoking
Non-current	225 (27.6)	1.00	1.00	ref.
Current	125 (44.0)	2.14^∗	1.52	(0.89–2.61)
Alcohol intake (units per week)
≤10	141 (29.1)	1.00	1.00	ref.
11–20	122 (31.1)	1.21	0.97	(0.53–1.78)
≥21	87 (43.7)	2.13^∗	1.54	(0.82–2.90)
Linear (per unit)		1.03^∗	1.02	(0.99–1.04)
Lifetime number of sexual partners
≤3	131 (19.1)	1.00	1.00	ref.
4–9	133 (32.3)	1.99^∗	1.52	(0.82–2.80)
≥10	86 (57.0)	5.43^∗	3.30	(1.70–6.40)
Linear (per partner)		1.08^∗	1.05	(1.00–1.10)
Number of sexual partners (previous 12 months)
0–1	159 (23.3)	1.00	1.00	ref.
≥2	189 (41.8)	2.50^∗	1.32	(0.74–2.36)
Anal intercourse
Never	273 (27.8)	1.00	1.00	ref.
Ever	77 (53.2)	2.92^∗	1.85	(1.02–3.36)
Condom use (previous four months)
Always	122 (20.5)	1.00	1.00	ref.
Never/sometimes	225 (40.0)	2.53^∗	1.93	(1.08–3.44)
Genital warts (self-report)
Never	332 (31.3)	1.00	1.00	ref.
Ever	15 (80.0)	8.47^∗	4.79	(1.10–20.91)
Chlamydia (self-report)
Never	335 (31.3)	1.00	1.00	ref.
Ever	13 (76.9)	7.82^∗	4.37	(1.04–18.32)

HPV = human papillomavirus; OR = odds ratio

†

Adjusted for age

‡

Adjusted for years of schooling, lifetime sexual partners, anal intercourse, recent condom use, self-reported genital warts and chlamydia

∗

P value <0.05

Number of female sexual partners was an important risk factor, particularly the lifetime number of sexual partners increased the risk of HPV infection (OR = 1.05; 95% CI: 1.00–1.10 per additional partner). In addition, anal intercourse with a female sexual partner increased the risk of HPV infection, the OR being 1.85 (95% CI: 1.02–3.36) for ever having had anal intercourse. Never or infrequent condom use in the last four months was associated with an increased risk of HPV positivity (OR = 1.93; 95% CI: 1.08–3.44). In addition, self-reported genital warts and genital Chlamydia infection increased the risk of HPV positivity in men (OR = 4.79; 95% CI: 1.10–20.91 and OR = 4.37; 95% CI: 1.04–18.32, respectively).

We stratified the analyses according to number of HPV types detected. This resulted in two analyses, one among men HPV-positive for one HPV type and one among men positive for two or more HPV types at baseline (Table 3). Men with 10 years or less of schooling had a higher risk for single-type infection (OR = 2.38; 95% CI: 1.22–4.64). An increased risk for prevalent multiple-HPV types was observed in current smokers, the association only being borderline significant after adjustment for potentially confounding factors. A significantly increased risk for multiple HPV types was also found with increasing alcohol intake (OR = 1.05; 95% CI: 1.01–1.09 per extra unit of alcohol per week). In contrast, no association with single HPV type infection was seen for smoking or alcohol.

Table 3

Determinants for single- or multiple-HPV types, respectively, among young Danish male conscripts

Variables	Singie HPV type n (% pos)	Multiple HPV types Single HPV type
Variables	Singie HPV type n (% pos)	OR^†	OR^‡	95% CI	n (% pos)	OR^†	OR^§	95% CI
Age (per year)		1.14	1.07	(0.84–1.38)		1.08	1.37	(0.92–2.04)
Years of schooling
≥11	191 (13.6)	1.00	1.00	Ref.	187 (11.8)	1.00	1.00	ref.
≤10	98 (30.6)	2.71^∗	2.38	(1.22–4.64)	84 (19.0)	1.76	1.92	(0.81–4.55)
Smoking
Non-current	195 (16.4)	1.00	1.00	ref.	180 (9.4)	1.00	1.00	ref.
Current	94 (25.5)	1.81	1.29	(0.63–2.64)	92 (23.9)	3.02^∗	2.22	(0.96–5.13)
Alcohol intake (units per week)
≤10	121 (17.4)	1.00	1.00	Ref.	107 (6.5)	1.00	1.00	ref.
11–20	104 (21.2)	1.35	0.87	(0.40–1.90)	98 (14.3)	2.59	3.10	(0.95–10.11)
≥21	62 (21.0)	1.40	0.81	(0.33–1.96)	67 (26.9)	5.98^∗	7.97	(2.41–26.35)
Linear (per unit)		1.01	0.99	(0.96–1.02)		1.05^∗	1.05	(1.01–1.09)
Lifetime number of sexual partners
≤3	117 (9.4)	1.00	1.00	Ref.	111 (4.5)	1.00	1.00	ref.
4–9	111 (18.9)	2.19^∗	1.99	(0.86–4.62)	107 (15.9)	4.02^∗	1.87	(0.56–6.23)
≥10	61 (39.3)	6.09^∗	3.45	(1.43–8.35)	54 (31.5)	9.87^∗	3.53	(0.98–12.74)
Linear (per partner)		1.07^∗	1.03	(0.98–1.08)		1.08^∗	1.02	(0.96–1.08)
Number of sexual partners (previous 12 months)
0–1	138 (11.6)	1.00	1.00	Ref.	129 (5.4)	1.00	1.00	ref.
≥2	149 (26.2)	2.84^∗	1.60	(0.72–3.52)	142 (22.5)	5.29^∗	4.20	(1.55–11.37)
Anal intercourse
Never	229 (14.0)	1.00	1.00	Ref.	221 (10.9)	1.00	1.00	ref.
Ever	60 (40.0)	4.11^∗	3.29	(1.59–6.81)	51 (29.4)	3.45^∗	2.33	(0.95–5.68)
Condom use (previous four months)
Always	111 (12.6)	1.00	1.00	Ref.	100 (3.0)	1.00	1.00	ref.
Never/sometimes	176 (23.3)	2.07^∗	1.28	(0.60–2.71)	170 (20.6)	8.37	10.84	(2.62–44.83)
Genital warts (self-report)
Never	278(18.0)	1.00	1.00	Ref.	260 (12.3)	1.00	1.00	ref.
Ever	8 (62.5)	7.11^∗	6.89	(1.37–34.62)	10 (70.0)	16.46^∗	30.91	(5.30–180.08)
Chlamydia (self-report)
Never	279 (17.6)	1.00	1.00	Ref.	265 (13.2)	1.00	1.00	ref.
Ever	9 (66.7)	10.40^∗	7.03	(1.45–34.03)	6 (50.0)	6.51^∗	1.86	(0.21–16.28)

HPV = human papillomavirus OR = odds ratio

†

Adjusted for age

‡

Adjusted for years of schooling, lifetime sexual partners, anal intercourse, genital warts and self-reported chlamydia

Adjusted for alcohol intake, recent sexual partners, recent condom use and genital warts

∗

P value <0.05

Number of sexual partners measured as recent partners, (i.e. partners within the last year) was strongly associated with multiple HPV types, OR = 4.20 (95% CI: 1.55–11.37 for ≥2 female sexual partners within the previous year versus 0–1 female sexual partner). In men with a single-type infection, lifetime number of sexual partners was a stronger determinant of HPV positivity (OR = 3.45; 95% CI: 1.43–8.35 for ≥10 lifetime sexual partners compared with ≤3 partners), whereas recent sexual partners showed no significant association. Ever having had anal intercourse was significantly associated with HPV positivity in men with a single-type infection (OR = 3.29; 95% CI: 1.59–6.81). The same tendency was observed in men with multiple HPV types, the association was, however, not statistically significant (OR = 2.33; 95% CI: 0.95–5.68). No significant association with condom use within the previous four months was observed in men with a single-type infection, but a strongly increased risk of multiple HPV types was observed in men who in the last four months used condoms infrequently or never (OR = 10.84; 95% CI: 2.62–44.83) after adjustment for confounding factors including number of recent sex partners.

A history of genital warts (OR = 6.89; 95% CI: 1.37–34.62) and Chlamydia trachomatis was associated with single HPV type infection (OR = 7.03; 95% CI: 1.45–34.03), but only genital warts were associated with multiple HPV types (OR = 30.91; 95% CI: 5.30–180.08).

Although the power of the study decreased markedly when we evaluated HR types separately, we tried to examine single and multiple HPV types in men only positive for HR HPV types. In general, the results were similar to the findings of single and multiple types without restrictions (data not shown).

Discussion

In our study of uncircumcised men aged 18–29 years the overall HPV prevalence was 33.4%, confirming the highly prevalent nature of HPV infection in men. A systematic review of the literature regarding HPV prevalence in men reports a prevalence ranging from 6.5 to 50.0% in studies with sampling at the corona and glans penis.¹⁴ In a study with extensive sampling of the anogenital area including the scrotum and the perianal region a prevalence of more than 60% was observed.¹⁵ A study from Finland in a setting similar to ours found an HPV prevalence of 26.2% among 432 conscripts when defining HPV positivity as either HPV PCR positive or HPV findings on peniscopy, (e.g. warts or flat lesions).⁷ More recently, a study derived from a clinical trial of the quadrivalent vaccine in men showed an overall prevalence of 21% in men with no more than five female partners at enrolment.¹⁶ Thus, as for women, the prevalence is dependent, among other things, on age distribution of the study population, the nature of the population, (e.g. general population, STI clinic clients) and the use of different sampling sites and sampling methods and consequently comparing overall HPV prevalence between populations is difficult.

HPV16, HPV6 and HPV18 which are all contained in the quadrivalent HPV vaccine were among the most common HPV types detected. HPV16 is also in other studies among men the commonest HPV type.^6,15,17,18 More than one-third of HPV-positive men were positive for at least one of the quadrivalent vaccine types. However, none of the men were positive for all four vaccine types and only a few men were positive for more than one of the vaccine types. This indicates that HPV vaccine in men even after initiation of sexual activity may also be worth considering not only to prevent transmission of HPV from men to women but also to reduce the incidence of genital warts as well as penile, anal and head and neck cancers in men.

Around one-third of the men had multiple-HPV types detected, ranging from 2 to 5 HPV types. Knowledge of the health consequences for men having multiple HPV types is limited, though some previous studies indicate that multiple HPV types in men are associated with increased risk of persistence,^10,11 and thus an increased risk of anogenital cancer may also be hypothesized. Furthermore, previous studies in women and men have observed that initially HPV-positive women/men are more likely to acquire new HPV types.^11,19,20 This may indicate that presence of HPV facilitates acquisition of new HPV types or alternatively that having multiple HPV types may be an indicator of higher susceptibility. We observed that sexual habits, notably recent number of sexual partners, were highly associated with risk of multiple HPV types. This indicates that recent exposure to different HPV types may also influence the presence of multiple HPV types. In further support of this hypothesis, we found a higher risk of multiple HPV types in men who used condoms infrequently compared with men who always used condoms in the last four months. Our finding that consistent condom use is associated with a decreased likelihood of being HPV-positive is in line with recent studies from the USA^21,22 and the Finnish study in conscripts although the latter considered condom use only in a univariate analysis.⁷

Having ever had anal intercourse was also a risk factor for prevalent HPV infection (only significant for single HPV type infection). This corresponds well with the fact that the anal mucosa, like the cervical mucosa, harbours HPV In a study conducted among heterosexual men without any experience of anal intercourse an almost 10% prevalence of HPV in the perianal region was detected.¹⁶ Among highly sexually active HIV-negative men having had receptive anal intercourse, the prevalence of HPV in the anal canal was found to be even higher, namely 57%.²³ In line with these findings, it is estimated that HPV causes more than 90% of all anal cancers in both women and men.²⁴

We found that a history of genital warts was significantly related to both single-type and multiple-type HPV infection; however, the association was stronger with the risk for multiple HPV types than with single type infection. This is in agreement with two previous studies examining the association between genital warts and HPV infection.^21,25 Hernandez et al. suggest that genital warts may serve as a ‘reservoir of infection’ where the virions remain on the mucosa after the visible infection has disappeared, a theory, which may also explain the high recurrence rate of genital warts. Alternatively, it may be hypothesized that genital warts act as an indicator of higher exposure to HPV and thereby cause strong association with multiple HPV types or that individuals who develop genital warts in spite of the fact that most HPV infections are transient and without symptoms, may be more susceptible.

In some previous studies, current smoking has been associated with multiple-type HPV and with persistence of HPV in men,^11,21 whereas past smoking has been associated with acquisition of HPV.²⁶ Our findings of an association with current smoking, although only borderline significant, may support a role of smoking for the risk of multiple HPV types. We observed that increasing weekly alcohol intake strongly increased the risk for multiple HPV types even after adjustment for confounders including sexual habits. As it has been suggested for smoking,¹ effect of alcohol intake may be due to an increase in susceptibility to HPV infection. However, it cannot be excluded that it may act as a proxy for unmeasured sexual behaviour.

There are some limitations to our study that may be considered, including relatively limited numbers of individuals in the analyses dividing the HPV positives into single-type and multiple-type infections. In addition, the study population has a narrow age range. Paying the participants for their participation may have helped increase the participation rate. However, the amount of money was limited so we do not expect it to have had a major impact. The amount of money was evaluated and approved by the Scientific Ethical Committee on the basis that this payment should be so limited that it would not be an important incitement to participate.

In conclusion, we found in accordance with previous findings in women that HPV is highly prevalent in our study population of young uncircumcised men, including the prevalence of multiple HPV types. Furthermore, our findings re-emphasize the importance of sexual transmission, with factors related to recent practice such as recent sexual partners and recent infrequent condom use being strong risk factors especially for having multiple HPV types. Interestingly, we found that factors which might be related to increased susceptibility of the individual, like alcohol intake, genital warts and to a lesser extent, smoking were strongly associated with having multiple HPV types. However, whether presence of multiple HPV types in men mainly are due to behavioural characteristics or whether men with multiple HPV types possess certain characteristics such as an impaired immune response that increases susceptibility still remains uncertain and needs further investigation.

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