Background: Despite recommendations for vaccination against hepatitis B virus (HBV) of men who have sex with men (MSM), most remain unvaccinated.
Goal: The goal of this study was to identify attitudes and beliefs associated with vaccination against HBV among black MSM.
Study Design: The Birmingham Vaccine Acceptance Questionnaire was used to collect data from gay bar patrons.
Results: Of the 143 participants, nearly 42% reported at least one dose of HBV vaccine. In multivariable analysis, characteristics associated with vaccination were a decreased perception of barriers to HBV vaccination (odds ratio [OR], 0.37; 95% confidence interval [CI], 0.22–0.61;P = 0.001); increased perceived medical severity (OR, 5.34; 95% CI, 2.38–11.96;P = 0.001) and personal severity (OR, 2.22; 95% CI, 1.38–3.56;P = 0.006) of HBV infection; and increased perceived general medical self-efficacy (OR, 9.22; 95% CI, 3.52–24.11;P = 0.0001) and personal self-efficacy (OR, 2.3; 95% CI, 1.14–4.63;P = 0.008) to complete the three-dose series.
Conclusions: Our findings underscore the need to increase vaccination through innovative approaches to reduce perceived barriers to vaccination while increasing perceived severity of HBV infection and self-efficacy to complete the vaccine series.
HEPATITIS B VIRUS (HBV) INFECTION continues to be one of the most frequently reported preventable diseases in the United States, despite the licensure of a vaccine in 1982. 1 In the United States, an estimated 240,000 new infections occur annually, 1 and currently an estimated 1.25 million individuals in this country are chronically infected with HBV. 2–5 Sequelae resulting from chronic HBV infection include cirrhosis of the liver and hepatocellular carcinoma, and an estimated 6,000 deaths occur annually from these complications. 6–9
Because HBV can be transmitted through sexual activity, 10 the U.S. Centers for Disease Control and Prevention (CDC) and the U.S. Gay and Lesbian Medical Association recommend vaccination against HBV for all men who have sex with men (MSM), 1,11 a group for whom HBV has been identified as one of the most important sexually transmitted diseases (STDs). 1,12–15 However, available national epidemiologic data and results of community-based HBV vaccination programs indicate that the majority of MSM are not vaccinated. 13,15,16
Estimates of the prevalence of previous HBV infection in this population range from 5% to 81%; prevalence of hepatitis B surface antigen (HBsAg) varies from 1% to 11%. 17,18 Self-reported vaccination rates among sexually active MSM are low, ranging from 11% to 48%. 12,15,18–23
Recent studies examining HBV infection by race indicate a substantially higher incidence of new HBV infections as well as a higher level of HBV prevalence among blacks. 2,5,24 Despite the low rates of vaccination among MSM and the increased incidence and prevalence among blacks, little is known about HBV vaccination acceptance that could help guide tailored intervention efforts 12,16,18,21–23,25,26. Although the association of race with disease most likely is a proxy for some other characteristic, 27,28 understanding vaccination behavior among subgroups is essential to ensure that appropriately tailored, effective intervention strategies are designed and implemented.
In this study, we sought to explore the psychosocial variables that may affect HBV vaccination acceptance among a conventional outreach sample of black MSM. Findings from this study may inform intervention efforts to increase vaccination rates among black MSM, a subsample of MSM that is particularly neglected in the HBV vaccination behavioral literature. 29 Findings from this study also may inform future interventions designed to enhance vaccination within this population as vaccines against HIV and hepatitis C become available.
Constructs from two of the most widely used behavior change theories 30 were integrated to identify theory-based correlates of HBV vaccination among a convenience sample of MSM. The theories used in this study of HBV vaccination included the health belief model (HBM) 30–34 and the social cognitive theory. 35–37 These theories have been used successfully to explain factors that contribute to health behavior and the mechanisms by which these factors operate. 30
Among adult and adolescent MSM, the HBM has been used to understand sexual risk behavior, 38–41 HIV testing, 42,43 HIV treatment initiation, 44 and risk-reduction intervention participation and completion. 45 When applied to HBV vaccination, the HBM postulates that in order for individuals to participate in a health behavior, they must believe that (1) they are personally susceptible to HBV infection (perceived susceptibility); (2) contracting HBV would have a negative impact on their lives (perceived severity); (3) getting vaccinated against HBV would be beneficial (perceived benefits); and (4) getting vaccinated is not discouraged by insurmountable barriers (perceived barriers).
Perceived self-efficacy is a central concept within the social cognitive theory and is considered to be its most important construct. 35,37 Perceived self-efficacy is defined as the conviction that one can successfully execute the behavior required to produce the desired outcome in various situations. 35–37 Among MSM, perceived self-efficacy has been used to understand HIV sexual risk reduction behavior. 38,41,46–48 When applied to HBV vaccination, self-efficacy is the confidence that an individual perceives himself or herself to have to complete the three-dose vaccination series despite various perceived barriers and limitations.
To the best of our knowledge, this is the first published study to investigate theory-based attitudes and beliefs about HBV vaccination among black MSM, a group at increased risk of exposure to HBV.
African American gay men in Alabama who perceived fewer barriers to vaccination, believed infection to be severe, and had confidence in their ability to complete the 3-dose series were more likely to be vaccinated against hepatitis B.
*Department of Public Health Services, Wake Forest University School of Medicine, Winston-Salem, North Carolina; and †Department of Behavioral Sciences and Health Education, Rollins School of Public Health, ‡Department of Medicine, Division of Infectious Diseases, School of Medicine, and §Emory Center for AIDS Research, Emory University, Atlanta, Georgia
Human subject review and oversight were provided by the Institutional Review Board of the University of Alabama at Birmingham.
Manuscript preparation was supported in part by the Community Health Scholars Program, funded by the W.K. Kellogg Foundation (to Scott D. Rhodes).
Reprint requests: Scott D. Rhodes, PhD, MPH, Wake Forest University School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157–1063. E-mail: Scott_Rhodes@UNC.edu
Received September 9, 2002,
revised December 23, 2002, and accepted December 30, 2002.
Data Collection Procedures
During November 2001, data were collected anonymously in a predominantly black, “gay” male bar in Birmingham, Alabama, USA. All bar patrons were asked to participate regardless of perceived gender or race by a trained recruiter, who explained the study and assessed sobriety of potential participants on the basis of established criteria 49 to ensure informed consent. Questionnaires were self-administered and completed in secluded areas of the bars to enhance participants’ valid reporting of sensitive behaviors. Participants were compensated $10.00 for completing the survey. The data were entered into an electronic database with use of double-entry procedures to assess and validate accuracy.
The Birmingham Vaccine Acceptance Questionnaire included 69 items. Items measured participants’ sociodemographic characteristics, including age, race/ethnicity (American Indian or Alaska Native; Asian; black; Hispanic or Latino; Native Hawaiian or Pacific Islander; or white), educational attainment, estimated yearly income, and health insurance coverage.
Sexual risk was measured by items that assessed the frequency of condom use during oral and anal intercourse with a male partner within the past 3 months and the number of sex partners during the past 30 days and lifetime. Items assessed whether participants had ever received a positive HIV serological test result. Items also assessed whether participants had ever or in the past 5 years been told that they had HIV disease or any other STD.
Items measured nonsexual risk behaviors as well, including international travel since 1995, because HBV vaccination is recommended for travel within some regions. 50–52 Items assessed participant history of injecting drugs or steroids, sharing injecting-drug equipment, and receiving blood or blood products.
Items assessed participant history of HBV awareness, vaccination, testing, and treatment. Vaccination against HBV was assessed by self-reported vaccination status, regardless of completion of the three-dose series (data have suggested that an incomplete vaccination regimen may confer adequate immunity in some individuals). 53–55
Theory-based, latent construct variables based on the HBM and the social cognitive theory, specifically related to HBV vaccination, were measured with 34 items comprising eight measures that have been identified through rigorous psychometric scale development. In brief, measurement development with use of a diverse sample of 358 MSM followed a two-step process.
First, standard procedures of principal component analysis (PCA) with Varimax rotation were employed to determine a factor structure for each scale on a slit half sample (n = 179). The scree test, 56 eigenvalues, 57 interpretability of the factors, 58,59 theoretical considerations, 60 factor loadings, 56,58,61 and Cronbach’s coefficient alpha 62 were used to define all factor structures. The remaining split-half (“hold-out”) sample (n = 179) was used for instrument confirmation analyses with AMOS, 63 a statistical package that is commonly used for structural equation modeling (SEM).
Confirmatory factor analysis (CFA) via SEM recently has become one of the primary methods of choice for measurement development. CFA recognizes the role of theory for establishing a structural model that organizes scale and subscale development. CFA permits evaluating the adequacy of a proposed factor structure. 64–66 Number of items per scale, sample items, and Cronbach’s coefficient alphas for the current study sample are presented in Table 1.
A final item assessed whether participants had completed the questionnaire previously. The response categories for each item within the questionnaire used binary, categorical, or Likert-scale responses to facilitate readability and administration.
SPSS for Windows 10.1 (SPSS, Chicago, IL) was used for data analysis. The Kolmogorov–Smirnov one-sample test 57 was performed to determine whether the data were normally distributed. All distributions were normal at P < 0.05.
All theory-based scales were dichotomized by median split and entered into a multivariate logistic regression model to test the independent contribution of each of the constructs while adjusting for the other constructs in the model. 67 Accordingly, adjusted odds ratios (ORs) and 95% CIs were calculated to assess the magnitude of association between theory-based predictors and self-reported vaccination.
Of the 179 participants who completed the survey, 167 were identified as MSM; of these, 143 self-identified as black; 5 as Hispanic or Latino; 5 as Asian; and 4 as white. Of the 143 black participants, the mean (±SD) age was 25.18 ± 6.1 years, with a range of 18 to 50 years. The majority of participants reported some college or more education (62.9%), yearly income of $20,000 or more (61.7%), and having private health insurance (59.0%).
Nearly 42% (n = 60) reported being vaccinated against HBV, while 18.9% (n = 27) reported never having heard of HBV. Over half of the participants reported 10 or more different lifetime male sex partners (n = 92), and fewer than half reported 2 or more different male sex partners within the past 30 days (n = 61). Nearly a third (n = 47) reported having had intercourse with females as well as males within the past 5 years.
When asked what percentage of the time they used condoms during intercourse, 7% of the participants reported condom use over half of the time when performing or receiving oral intercourse, and 50% of the participants reported using a condom over half the time during insertive or receptive anal intercourse.
Not including HIV seropositivity, over 13% of this sample (n = 19) reported a lifetime history of at least one STD diagnosis, and 6.3% (n = 9) reported that they had received at least one STD diagnosis within the past 5 years. Almost 6% (n = 8) reported a positive HIV antibody test result. About 4% of the sample (n = 6) reported having received blood or blood products before 1992, and 5.6% (n = 8) reported ever having injected drugs or steroids; only two participants reported ever having shared injecting drug equipment.
Attitudes and Beliefs About HBV Infection and Vaccination
Table 2 displays the OR, 95% CI, and significance level between HBV vaccination and the independent contribution of each theory-based construct. The predictive power of the overall theory-based model (chi-square = 86.32;P = 0.0001) was high, correctly classifying 79% of the participants in their self-reported vaccination status categories.
Participants who perceived low levels of practical barriers to HBV vaccination were 2.7 times more likely to be vaccinated against HBV than those who perceived high levels of practical barriers to HBV vaccination. Participants who perceived the medical outcomes of HBV infection to be highly severe were 5.3 times more likely to self-report vaccination against HBV than those who perceived low levels of general medical severity, and those who perceived high levels of personal severity of HBV were 2.2 times more likely to self-report HBV vaccination. Participants who perceived high levels of general medical self-efficacy to complete the three-dose series were nine times more likely to self-report HBV vaccination than those who perceived low levels of general medical self-efficacy to complete the series, and participants who perceived high levels of personal self-efficacy to complete the three-dose series were twice as likely to self-report HBV vaccination than those who perceived low levels of personal self-efficacy.
Enhancing awareness and facilitating vaccination among populations at risk for HBV infection are urgently needed. Although more than 40% of participants in this study reported vaccination, almost 20% reported no information about hepatitis. Furthermore, many participants reported engaging in behaviors that put them and their sex partners at risk for HBV infection. Given that HBV transmission can result from mucous membrane exposure to infectious body fluids, including semen, 10 the low level of vaccination and the high levels of risk behaviors, such as inconsistent condom use, suggest that the failure to vaccinate this high-risk population is a missed opportunity to prevent disease.
Within our sample of black MSM, lower scores for perceived practical barriers to HBV vaccination were associated with HBV vaccination. Thus, interventions to increase vaccination among these MSM may focus on educating MSM about insurance coverage for vaccination, identifying locations for vaccination administration, and reducing the out-of-pocket expense of vaccination against HBV.
Unlike other studies that have found an association between HBV vaccination and health care provider communication about patients’ sexual orientation and risk, 12,22 in the current study we did not find this to be a significant predictor of HBV vaccination after accounting for the other predictors in the model. In part, this finding may be due to efforts to use social networks for vaccination efforts that do not require individual risk disclosure. Using the social networks of black MSM, promoters of vaccination services, such as health department staff, can reach eligible men for HBV vaccination without requiring sexual orientation or sexual risk disclosure. Using a diffusion-of-innovations 68 approach has been shown to be successful in HIV prevention intervention design among MSM 69,70 and could be tested empirically for the promotion of HBV vaccination, especially among men who may perceive social stigma associated with their same-sex behavior.
Furthermore, because recommendation by a health care provider has been found to be a strong predictor of preventive behavior in general, 71–73 the importance of the health care provider in promoting preventive behavior among MSM cannot be discounted on the basis of this study. In fact, the provider may influence other attitudes and beliefs that have been found to be predictive of HBV vaccination.
The finding that vaccinated participants perceived a higher level of severity of HBV infection reflects both medical and personal perceptions of severity. Because each subscale was included in the multivariable logistic model, efforts to increase vaccination rates among MSM must include messages that address the medical sequelae of HBV infection as well as the personal relevance of HBV infection (e.g., effects on diet and one’s peace of mind).
General medical and personal self-efficacy also was found to be predictive of vaccination status in the multivariable model. Participants who reported more confidence in overcoming fears of needles, fears of vaccinations, and their distrust for the government were more likely to report vaccination, as were participants who reported more confidence in overcoming the embarrassment of talking about their sexual behavior with providers, worries about HBV vaccine safety and possible side effects, and concerns such as time and money.
Thus, to increase vaccination among unvaccinated MSM, trust must be built between the medical community and the black MSM community in order to overcome histories such as the Tuskegee Syphilis Study and to ensure utilization of health-promoting technologies. The emphasis on vaccine safety also is particularly important, given the negative publicity surrounding potential deleterious side effects of the HBV vaccine. 74,75
The negative association between HBV vaccination and perceived susceptibility to infection may be a result of vaccinated individuals reporting low perceived susceptibility as a result of their vaccination status; those who have been vaccinated do not believe they are susceptible to infection on the basis of their vaccination status.
The current study is not without limitations. First, the observed associations are based on cross-sectional data. Additional studies with a prospective cohort design will be necessary to evaluate the significance and stability of these findings over time. Furthermore, the results of this study may not apply to the general population of MSM. However, the degree of fit between a sample and a target population about which generalizations can be made is a common challenge in many studies; in fact, nearly all studies of sexual behavior among MSM are based on nonrandom, self-selected samples. 76–78
Lending support for the validity of this study, the vaccination rate we observed is within the range of what other investigators have reported. 12,15,18–23 Although we utilized a self-administered format that may minimize response bias and included techniques found to increase validity of self-reported behavior, 79 these results nevertheless are based on self-reported data, with their potential limitations. 80
Understanding HBV vaccination among black MSM not only is crucial for the development and evaluation of tailored interventions aimed at increasing vaccination against HBV but also provides the framework for developing future vaccination strategies for conditions such as HIV disease and hepatitis C. Whereas we have reported on psychosocial predictors of HBV vaccination based on a sample of black MSM, a group about whom much behavioral data are lacking, 81,82 subsequent studies must explore further the potential impact of increased access to heath care; reduced costs for vaccination services; and vaccination opportunities in untraditional venues such as bars, bath houses, coffee shops, gyms, and house parties.
Hepatitis B is one of only two vaccine-preventable STDs (hepatitis A is the other), but after 20 years of HBV vaccine licensure, many MSM remain unvaccinated. Much is still unknown about the factors that influence MSM vaccination behavior. Focus must be placed on increasing our understanding of the factors that affect vaccination acceptance in order to develop innovative and well-tailored strategies to increase vaccination rates among MSM.
1. Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines: 2002. MMWR Morb Mortal Wkly Rep 2002; 51: 1–80.
2. McQuillan GM, Coleman PJ, Kruszon-Moran D, Moyer LA, Lambert SB, Margolis HS. Prevalence of hepatitis B virus infection in the United States: the National Health and Nutrition Examination Surveys, 1976 through 1994. Am J Public Health 1999; 89: 14–18.
3. Lee WM. Hepatitis B virus infection. N Engl J Med 1997; 337: 1733–1745.
4. Meheus A. Risk of hepatitis B in adolescence and young adulthood. Vaccine 1995; 13( suppl 1): S31–S34.
5. Coleman PJ, McQuillan GM, Moyer LA, Lambert SB, Margolis HS. Incidence of hepatitis B virus infection in the United States, 1976–1994: estimates from the National Health and Nutrition Examination Surveys. J Infect Dis 1998; 178: 954–959.
6. van Leeuwen DJ, Dadrat A. Viral hepatitis and its imitators. In: Blackwell RE, ed. Women’s Medical Text. Boston: Blackwell Science, 1996: 324–338.
7. Schafer DF, Sorrell MF. Hepatocellular carcinoma. Lancet 1999; 353: 1253–1257.
8. Koff RS. Advances in the treatment of chronic hepatitis. JAMA 1999; 282: 511–512.
9. Regev A, Schiff ER. Viral hepatitis A, B, and C. Clin Liver Dis 2000; 4: 47–71.
10. Chin J, ed. Control of Communicable Diseases Manual. 16th ed. Washington, DC: American Public Health Association, 2000.
11. Gay and Lesbian Medical Association. Healthy People 2010 Companion Document for Lesbian, Gay, Bisexual, and Transgender (LGBT) Health. San Francisco, CA: Gay and Lesbian Medical Association, 2001.
12. Dufour A, Remis RS, Alary M, et al. Factors associated with hepatitis B vaccination among men having sexual relations with men in Montreal, Quebec, Canada. Omega Study Group. Sex Transm Dis 1999; 26: 317–324.
13. Institute of Medicine, Committee on Prevention and Control of Sexually Transmitted Diseases. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: National Academy Press, 1997.
14. Kingsley LA, Rinaldo CR, Lyter DW, Valdiserri RO, Belle SH, Ho M. Sexual transmission efficiency of hepatitis B virus and human immunodeficiency virus among homosexual men. JAMA 1990; 264: 230–234.
15. Kane M. Epidemiology of hepatitis B infection in North America. Vaccine 1995; 13( suppl 1): S16–S17.
16. MacKellar DA, Valleroy LA, Secura GM, et al. Two decades after vaccine license: hepatitis B immunization and infection among young men who have sex with men. Am J Public Health 2001; 91: 965–971.
17. Brook MG. Sexual transmission and prevention of the hepatitis viruses A-E and G. Sex Transm Infect 1998; 74: 395–398.
18. Seage GR, Mayer KH, Lenderking WR, et al. HIV and hepatitis B infection and risk behavior in young gay and bisexual men. Public Health Rep 1997; 112: 158–167.
19. Katz M. Undervaccination for hepatitis B among young men who have sex with men: San Francisco and Berkeley, California. MMWR Morb Mortal Wkly Rep 1996; 45: 215–217.
20. Loke RH, Murray-Lyon IM, Balachandran T, Evans BA. Screening for hepatitis B and vaccination of homosexual men. BMJ 1989; 298: 234.
21. Neighbors K, Oraka C, Shih L, Lurie P. Awareness and utilization of the hepatitis B vaccine among young men in the Ann Arbor area who have sex with men. J Am Coll Health 1999; 47: 173–178.
22. Rhodes SD, DiClemente RJ, Yee LJ, Hergenrather KC. Correlates of hepatitis B vaccination in a high-risk population: an Internet sample. Am J Med 2001; 110: 628–632.
23. Rhodes SD, DiClemente RJ, Yee LJ, Hergenrather KC. Hepatitis B vaccination in a high-risk MSM population: the need for vaccine education. Sex Transm Infect 2000; 76: 408–409.
24. Siegel D, Alter MJ, Morse S. Hepatitis B virus infection in high-risk inner-city neighborhoods in San Francisco. Hepatology 1995; 22: 44–49.
25. Rhodes SD, Hergenrather KC. Exploring hepatitis B vaccination acceptance among young men who have sex with men: facilitators and barriers. Prev Med 2002; 35: 128–134.
26. Yuan L, Robinson G. Hepatitis B vaccination and screening for markers at a sexually transmitted disease clinic for men. Can J Public Health 1994; 85: 338–341.
27. Bhopal R. Is research into ethnicity and health racist, unsound, or important science? BMJ 1997; 314: 1751–1756.
28. Bhopal R. Revisiting race/ethnicity as a variable in health research. Am J Public Health 2002; 92: 156–157.
29. Yee LJ, Rhodes SD. Understanding correlates of hepatitis B virus vaccination in men who have sex with men: what have we learned? Sex Transm Infect 2002; 78: 374–377.
30. Kohler CL, Grimley D, Reynolds K. Theoretical approaches guiding the development and implementation of health promotion programs. In: Raczynski JM, Diclemente RJ, eds. Handbook of Health Promotion and Disease Prevention. New York, NY: Kluwer Academic/Plenum Publishers, 1999: 23–49.
31. Janz NK, Becker MH. The Health Belief Model: a decade later. Health Educ Q 1984; 11: 1–47.
32. Rosenstock IM. Historical origins of the health belief model. Health Educ Monogr 1974; 2: 1–8.
33. Rosenstock IM. The health belief model and preventive health behavior. In: Becker MH, ed. The Health Belief Model and Personal Health Behavior. Thorofare, NJ: Charles B. Slack, 1974: 27–59.
34. Strecher VJ, Rosenstock IM. The health belief model: explaining health behavior through expectancies. In: Glanz K, Lewis FM, Rimer BK, eds. Health Behavior and Health Education: Theory, Research, and Practice. 2nd ed. San Francisco, CA: Jossey-Bass, 1997: 41–59.
35. Bandura A. Self-Efficacy: The Exercise of Control. New York, NY: WH Freeman and Sons, 1997: 1–78.
36. Bandura A. Social foundations of thought and action: a social cognitive theory. Englewood Cliffs, NJ: Prentice-Hall, 1986: 390–453.
37. Bandura A. Self-efficacy mechanism in human agency. Am Psychol 1982; 37: 122–147.
38. Aspinwall LG, Kemeny ME, Taylor SE, Schneider SG, Dudley JP. Psychosocial predictors of gay men’s AIDS risk-reduction behavior. Health Psychol 1991; 10: 432–444.
39. Dawson J, Fitzpatrick R, Boulton M, McLean J, Hart G. Predictors of high risk sexual behaviour in gay and bisexual men. Soz Praventivmed 1992; 37: 79–84.
40. Simon PM, Morse EV, Balson PM, Osofsky HJ, Gaumer HR. Barriers to human immunodeficiency virus related risk reduction among male street prostitutes. Health Educ Q 1993; 20: 261–273.
41. Wulfert E, Wan CK, Backus CA. Gay men’s safer sex behavior: an integration of three models. J Behav Med 1996; 19: 345–366.
42. Maguen S, Armistead LP, Kalichman S. Predictors of HIV antibody testing among gay, lesbian, and bisexual youth. J Adolesc Health 2000; 26: 252–257.
43. Povinelli M, Remafedi G, Tao G. Trends and predictors of human immunodeficiency virus antibody testing by homosexual and bisexual adolescent males, 1989–1994. Arch Pediatr Adolesc Med 1996; 150: 33–38.
44. DiFranceisco W, Kelly JA, Sikkema KJ, Somlai AM, Murphy DA, Stevenson LY. Differences between completers and early dropouts from 2 HIV intervention trials: a health belief approach to understanding prevention program attrition. Am J Public Health 1998; 88: 1068–1073.
45. Gold RS, Ridge DT. “I will start treatment when I think the time is right”: HIV-positive gay men talk about their decision not to access antiretroviral therapy. AIDS Care 2001; 13: 693–708.
46. Dilley JW, McFarland W, Sullivan P, Discepola M. Psychosocial correlates of unprotected anal sex in a cohort of gay men attending an HIV-negative support group. AIDS Educ Prev 1998; 10: 317–326.
47. Miller RL. Assisting gay men to maintain safer sex: an evaluation of an AIDS service organization’s safer sex maintenance program. AIDS Educ Prev 1995; 7( 5 suppl): 48–63.
48. Semple SJ, Patterson TL, Grant I. Partner type and sexual risk behavior among HIV positive gay and bisexual men: social cognitive correlates. AIDS Educ Prev 2000; 12: 340–356.
49. Sy FS, Rhodes SD, Choi ST, et al. The acceptability of oral fluid testing for HIV antibodies. A pilot study in gay bars in a predominantly rural state. Sex Transm Dis 1998; 25: 211–215.
50. Hall AJ. Hepatitis in travellers: epidemiology and prevention. Br Med Bull 1993; 49: 382–393.
51. Levin JH, Clarke PD. Travel vaccines: a review of current thinking. Br Med Bull 1993; 49: 326–347.
52. Steffen R. Hepatitis A and hepatitis B: risks compared with other vaccine preventable diseases and immunization recommendations. Vaccine 1993; 11: 518–520.
53. Lee SD, Chan CY, Yu MI, et al. A two dose combined hepatitis A and B vaccine in Chinese youngsters. J Med Virol 1999; 59: 1–4.
54. Marsano LS, West DJ, Chan I, et al. A two-dose hepatitis B vaccine regimen: proof of priming and memory responses in young adults. Vaccine 1998; 16: 624–629.
55. Wistrom J, Ahlm C, Lundberg S, Settergren B, Tarnvik A. Booster vaccination with recombinant hepatitis B vaccine four years after priming with one single dose. Vaccine 1999; 17: 2162–2165.
56. Cattell R. The meaning and strategic use of factor analysis. In: Cattell RB, ed. Handbook of Multivariate Experimental Psychology. Chicago, IL: Rand McNally, 1966: 174–233.
57. Kleinbaum DG, Kupper LL, Muller KE, Nizam A. Applied Regression Analysis and Other Multivariate Methods. 3rd ed. Pacific Grove, CA: Brooks/Cole, 1998: 212–280.
58. Pedhazur EJ, Schmelkin LP. Measurement, Design, Analysis: An Integrated Approach. Hillsdale, NJ: Lawrence Erlbaum Associates, 1991: 590–740.
59. Tabachnick BG, Fidell LS. Using Multivariate Statistics. 4th ed. Needham Heights, MA: Allyn and Bacon, 2001: 582–771.
60. Bryant FB, Yarnold PR. Principle components analysis and exploratory and confirmatory factor analysis. In: Grimm LG, Yarnold PR, ed. Reading and Understanding Multivariate Statistics. Washington, DC: American Psychological Association, 1997: 99–136.
61. Nunnally JC. Introduction to Psychological Measurement. New York, NY: McGraw Hill, 1970.
62. Cronbach LJ. Coefficient alpha and the internal structure of tests. Psychometrika 1951; 16: 297–334.
63. Arbuckle JL, Wothke W. AMOS 4.0: User’s Guide. Chicago, IL: SmallWaters Corporation, 1999.
64. Bentler PM. Comparative fit indexes in structural models. Psychol Bull 1990; 107: 238–246.
65. Bentler PM, Bonett DG. Significance tests and goodness of fit in the analysis of covariance structures. Psychol Bull 1980; 88: 588–606.
66. Bollen KA. A new incremental fit index for general structural equation models. Sociol Methods Res 1989; 17: 303–316.
67. Hosmer DW, Lemeshow S. Applied Logistic Regression. New York, NY: John Wiley & Sons, 1989.
68. Rogers EM. Lessons for guidelines from the diffusion of innovations. Jt Comm J Qual Improv 1995; 21: 324–328.
69. Kelly JA, Murphy DA, Sikkema KJ, et al. Randomised, controlled, community-level HIV-prevention intervention for sexual-risk behaviour among homosexual men in US cities. Community HIV Prevention Research Collaborative. Lancet 1997; 350: 1500–1505.
70. Kelly JA. HIV prevention interventions with gay or bisexual men and youth. AIDS 2000; 14( suppl 2): S34–S39.
71. Goldstein MG, DePue J, Kazura A, Niaura R. Models of provider-patient interaction: applications to health behavior change. In: Shumaker SA, Schron EB, Ockene JK, McBee WL, eds. The Handbook of Health Behavior Change. 2nd ed. New York, NY: Springer, 1998: 85–113.
72. Bean P. The AIDS battle fatigue syndrome: what’s challenging medication adherence in HIV? Am Clin Lab 2001; 20: 11–13.
73. Riffe HA, Kaplan L. HIV prevention in challenging subcultures: reaching rural freshmen in university orientation classes. J HIV/AIDS Prev Educ Adolesc Children 2001; 4: 19–32.
74. Marshall E. A shadow falls on hepatitis B vaccination effort. Science 1998; 281: 630–631.
75. Ascherio A, Zhang SM, Hernan MA, et al. Hepatitis B vaccination and the risk of multiple sclerosis. N Engl J Med 2001; 344: 327–332.
76. Laumann EO, Gagnon JH, Michaels S. The Social Organization of Sexuality: Sexual Practices in the United States. Chicago: University of Chicago Press, 1994.
77. Rhodes SD, DiClemente RJ, Cecil H, Hergenrather KC, Yee LJ. Risk among men who have sex with men in the United States: a comparison of an Internet sample and a conventional outreach sample. AIDS Educ Prev 2002; 14: 41–50.
78. Ross MW, Tikkanen R, Mansson SA. Differences between Internet samples and conventional samples of men who have sex with men: implications for research and HIV interventions. Soc Sci Med 2000; 51: 749–758.
79. Fishbein M, Pequegnat W. Evaluating AIDS prevention interventions using behavioral and biological outcome measures. Sex Transm Dis 2000; 27: 101–110.
80. Pequegnat W, Fishbein M, Celentano D, et al. NIMH/APPC workgroup on behavioral and biological outcomes in HIV/STD prevention studies: a position statement. Sex Transm Dis 2000; 27: 127–132.
81. Kraft JM, Beeker C, Stokes JP, Peterson JL. Finding the “community” in community-level HIV/AIDS interventions: formative research with young African American men who have sex with men. Health Educ Behav 2000; 27: 430–441.
82. Stokes JP, Peterson JL. Homophobia, self-esteem, and risk for HIV among African American men who have sex with men. AIDS Educ Prev 1998; 10: 278–292.