These data are among the first to describe HBV seroprevalence in a large cohort of predominantly HIV-infected women in the United States. Not unexpectedly, given the similar modes of transmission of HIV and HBV infection, the 1500 women with HIV infection had a prevalence of HBV infection that was nearly twice that of HIV-uninfected women. However, our study suggests decreasing trends in HBV infection. The low prevalence of hepatitis B surface antigenemia in HIV-infected women enrolled from 1994 through 1995 (4%) was even lower in women enrolled from 2001 through 2002 (<1%). Another large multisite study reported a 4.6% prevalence of chronic HBV infection in HIV-infected women during the period from 1998 through 2001, using chart review and not serological evidence [13
]. Overall, HIV-infected women have a lower prevalence of chronic HBV infection than the 8%–9% prevalence reported in men from 2 large multisite HIV cohort studies [4
]. However, our serological data has identified several areas of concern.
First, our cohort of high-risk women had a low prevalence of vaccine immunity, suggesting either a lack of vaccination, failure to complete the vaccination series, or an inability to develop an adequate immune response [14
]. More than one-half of women appeared to be eligible for vaccination on the basis of negative serological test results. Although the raw prevalence of vaccine immunity was higher in the women who joined the cohort in 2001 and 2002, the proportion of HIV-infected women eligible for vaccination increased due to an overall decrease in HBV infection among newly enrolled women. The increased numbers of women eligible for vaccination may also reflect the fact that some women in our cohort were not recruited from clinics and thus may not have received routine primary care.
Second, 37% of HIV-infected women in our study with positive anti-HBc serological test results had an isolated anti-HBc pattern, which may be of concern in those with HIV infection because of the increased prevalence of detectable HBV DNA in HIV-infected patients with an isolated anti-HBc pattern, leading to an increased risk of cirrhosis and decreased survival time. Two studies [15
] found that 35%–60% of HIV-infected patients with anti-HBc alone had detectable HBV DNA levels. In a longitudinal study [15
], 90% of 57 patients with an isolated anti-HBc pattern had HBV DNA detected at least once from an average of 3.5 samples during a median follow-up period of 31 months. In another study [16
], 37 of 42 patients with anti-HBc alone had a persistent isolated anti-HBc pattern, and HBV DNA was detected in 35% of these 37 patients. However, another recent cross-sectional study [17
] found that only 2% of HIV-infected patients with anti-HBc alone had detectable HBV DNA levels at baseline. A 10% prevalence of detectable HBV DNA among those with anti-HBc alone has been commonly reported in the general population [18
]. Although our prevalence of isolated anti-HBc pattern is comparable to results reported in other studies involving groups mostly composed of HIV-infected men [15
], HIV-uninfected women in our cohort had a 32% prevalence of anti-HBc pattern, which is higher than the 10%–20% reported in HIV-uninfected persons with positive HBV markers from the United States and Europe [18
]. Finally, small studies also suggest an increased risk of cirrhosis in those with the isolated anti-HBc pattern and concurrent HCV infection, regardless of HIV infection status [16
]. Women in our cohort may be at particular risk of cirrhosis because of the high prevalence of concurrent HCV infection.
Our findings suggest that antibodies to HSV-2, a history of syphilis, and high-risk sexual behaviors are important risk factors that are associated with HBV infection, even among women with a history of IDU. Genital ulcers may facilitate the acquisition of HBV, have been demonstrated to facilitate the acquisition of HIV infection [21
], and may also be associated with high-risk behavior. Nonulcerative STDs are more likely to only indicate high-risk sexual behavior than to play a causal role. In our multivariate analysis, chlamydia and gonorrhea no longer appeared to be associated with HBV infection in women reporting a history of non-IDU. In contrast to other studies involving men and women [7
], anal sex was associated with a decreased risk of HBV infection in women with a history of IDU and was not strongly associated in the other 2 drug use groups. In a large multisite study of predominantly HIV-uninfected female sex workers [7
], anal sex was associated with HBV infection only among women without a history of IDU. Our findings are difficult to interpret; perhaps the sexual partners of those with a history of IDU are more likely to use condoms, given the increased risk of disease transmission.
Limitations of the study include its cross-sectional design. It is not clear whether the high-risk behavior occurred before or after HBV transmission. Another limitation of our study is the possible underreporting of sensitive risk behaviors, as demonstrated in the strong correlation we found between infection with HIV, HCV, and HBV in women who reported never using illicit drugs. HCV is transmitted more efficiently via the parenteral than the sexual route [24
]. The cross-sectional design also does not enable us to discern the temporal relationship between infection with HBV, HIV, and/or HCV. Use of self-reporting of STDs—particularly of chlamydia and gonorrhea, which are often asymptomatic in women—may also underestimate the effect of nonulcerative STDs on HBV infection.
Finally, data regarding frequency and duration of drug use, receptive sharing of needles, sharing of other drug-injecting equipment, and whether or not anal sex was protected was not obtained. Despite these limitations, our study represents one of the largest studies to investigate the prevalence and predictors of HBV in a cohort of predominantly HIV-infected women.
Reasons for the low prevalence of vaccine immunity in our cohort need to be studied, including whether HBV vaccine was administered, whether vaccination was completed, and, if completed, whether it was successful in developing immunity. The impact of occult HBV infection in our cohort of women, many of whom were also infected with HCV, must be further studied, including whether there is an accelerated progression to cirrhosis, as well as an increased risk of antiretroviral-associated hepatotoxicity.
HBV infection in injection drug users has been commonly attributed to risk behaviors directly associated with IDU, including the sharing of needles, but prevention of sexual transmission of HBV infection must not be overlooked. Preventing sexual transmission of HBV should be a major focus for all high-risk groups, and HBV vaccination should be routinely offered to those presenting with sexually transmitted diseases, especially genital ulcer disease [24