In this study, of 129 IDUs, four subjects were HBsAg positive (3.1%). In Khodadadizade et al. (2005), of 180 subjects five were HBV infected from whom three subjects were IDUs (
19). In Nikkhooy et al. study in Ahvaz, South-west of Iran conducted in 2004, 1.5% of 258 IDUs who were hospitalized in Razi Hospital were positive for HBsAg (
20). In another study, 970 IDU male prisoners were examined by Daneshmand et al. in 2009 in Esfahan, central Iran, and 32 subjects (3.3%) were positive for HBsAg. Daneshmand et al. study concluded that the longer duration of being incarcerated is associated with higher prevalence of HBV infection (
18). In another descriptive analytical study on 133 IDUs, 8 (6.2%) were HBV positive cases; a strong correlation between the use of shared needle and HBV infection was demonstrated (P < 0.05) (
21). Also, in the research by Nokhodian et al. (2012) on female prisoners in Esfahan, results showed that there is no association between the number of arrests and serological HBV markers; their study was limited on one hand by the number of cases that was only 163 and on the other hand it was only conducted on females (
22). Another study on females with illegal social behaviors in Esfahan showed the same results, that demonstrated no association between having prison history and HBV infection (
23). In a study in Shahrekord, located in West of Iran, by Khosravani et al. (2012) of 158 IDUs, 3.2% were HBsAg positive (
24). The prevalence of HBsAg among male IDUs in Tehran was reported to be 5.8%, whereas in Zahedan, South-east of Iran, it was 19.3% among hospitalized IDUs (
25). In another study, in Ahvaz, South-west of Iran, HBsAg prevalence was 3.6% among hospitalized drug users (
26). In Amin-Esmaeili et al. (2012) study on IDUs, in Tehran, the prevalence of past or current HBV infection had a high rate (46.1%), that was mainly correlated with history of imprisonment and drug use of more than 10 years (
17). In some reports from Iran (
27) and other countries regarding imprisonment (
28,
29), the frequency (
30) and duration of drug injection (
28,
31) are demonstrated as risk factors for HBV infection. Mir-Nasseri et al. (2011) study in Tehran, showed that the prevalence of HBsAg was 3.7% among 518 IDUs (
27), they showed that incarceration increased the risk of co-infection by 7.5 folds. This result was confirmed by a similar study by Zamani et al. (2005) (
32) on IDUs, and showed that infection was strongly associated with a history of shared drug injection inside prison, whereas it was not significantly related to shared drug injection outside the prison.
In Tofigi et al. study on cadaver of 400 intravenous drug users in Tehran, seroprevalence of HBsAg was 27.5% (
3). Merat et al. (2000) (
33), Farhat et al. (2003) (
34) and Sharif et al. (2009) (
35) reported a rate of 1.3%-4%; hepatitis virus infection in IDUs population was associated with sharing injection instruments and a long duration of prison stay and drug usage. Studies from other parts of the world, such as Brazil by Stief et al. (2010) (
36) and Berlin showed similar results, as they concluded that positive history of imprisonment is associated with 1.9 fold and 1.5 fold increase in the risk of HBV seropositivity, respectively. Their studies showed that history of syringe sharing in prison was associated with HBV, HCV and HIV infections. A research done by Nguyen et al. (2006), estimated the prevalence of HBV among IDUs in Australia to be 2% - 3%, in this study long term injection, having been to prison, and injecting in prison were independently associated with HBV infection (
37). There are also reports of greater than 50% prevalence of HBV among IDUs in other countries around the world such as Germany, Georgia and Bulgaria (
28,
38,
39).
Different studies showed that the prevalence of HBV in Europe and America is respectively more than those of Asia and the Middle East. According to previous studies, the prevalence of HBV among IDUs in Kopenhak drug users, Mexican and Denmark prisoners as well as Spain drug users was 64%, 61.1%, 64% and 67.3% (
40-
42), respectively, while the prevalence of HBsAg was reported to be 6.2% in Bangladesh (
43) and the rate of HBsAg positivity among IDUs in Kabul was demonstrated to be 6.5% (
44) and for Karachi,7.5% (
45). In Mirahmadzade et al. (2004) study on IDUs in Shiraz, South of Iran, HBV prevalence was reported to be 3% among the subjects (
46). In another study by Javadi et al. (2006) among IDU prisoners in central parts of Iran, the prevalence of HBsAg was 3.5% (
47). Rahimi-Movaghar study (2010) on 899 IDUs recruited in Tehran from treatment and harm reduction facilities and from drug users hangouts in public areas in 2007, showed 30.9% HBsAg positivity among these subjects (
48). As mentioned before, in the current study the prevalence of HBsAg among IDUs was 3.1% which is slightly lower than those reported from Tehran, Ahvaz, Shahrekord or other parts of Iran (
3,
20,
24,
26) (
Table 4).
Low rate of HBsAg positivity in this study might be reflected by HBV vaccination; in this study of 98 subjects, 58.2% had a history of HBV vaccination. The study of Khosravani et al. (2012) (
24), showed a similar low prevalence for HBsAg positivity among high risk groups, same as IDUs in South-west of Iran studied by Khosravani et al. (2012), where it was concluded that this result may be due to HBV vaccination in that area. It is interesting to note that national levels of 1st (HBV1), 2nd (HBV2) and 3rd (HBV3) dose coverage in Iran have been reported to be 98.9%, 98.8% and 98.4%, respectively (
53). After employment of the HBV vaccination in the Iranian national program of Immunization, and the expanded Program of Immunization (EPI) since 1993, the prevalence of HBV has decreased throughout the country (
33,
54). Another possibility for reduction in prevalence of HBsAg in our study can be due to harm reduction programs that are provided in DICs, since 2005 there have been continuous attempts to raise coverage of harm reduction intervention in Iran (
17). These findings can be a result of the scaling-up of harm reduction facilities such as NSP and MMT that started from 2002 and have been expanded since 2005 in Tehran. A considerable number of IDUs are covered under harm-reduction programs, either in DICs or in prison (
55). These results present a good opportunity to receive services for HBV patients to decrease exposure to contaminated blood, as well as risk reduction in high risk behaviors. Drug use is often a hidden behavior in society, and drug users are a kind of hard-to-reach group; therefore, selecting a representative sample of drug users in a geographical area is difficult. Additionally in this study, only IDUs in Tehran were involved, and the results may not be generalized to the entire Iranian IDU population. Due to difficulty in approaching IDUs as a hard-to-reach group,
we could not gain access to female groups; therefore, further studies are required to examine the studied high risk issue among females. In conclusion, fewer infected cases found in this study promises that in case of performing on-time detriment prevention and decreasing measures will cause future satisfying results in this case.