Immunogenicity, reactogenicity and adherence with hepatitis A vaccination among drug users
Introduction
Hepatitis A is an acute, usually self-limiting infection of the liver caused by hepatitis A virus (HAV). HAV infection occurs throughout the world, affecting 1.5 million people annually. HAV infection is highly correlated with poor social and economic conditions (WHO, 2000, CDC, 1999).
Although blood-borne transmission of HAV occurs, the increased risk for HAV infection among drug users (DUs) may be due to factors other than parenteral transmission, such as crowding and poor hygiene and contaminated drug preparations (WHO, 2000, CDC, 1999).
The World Health Organization has stated that, in developed countries, hepatitis A vaccination should be considered for specific high-risk populations such as injecting DUs (WHO, 2000). The Advisory Committee on Immunization Practices of the Centers for Disease Control and Prevention recommends hepatitis A vaccination for injecting DUs (CDC, 1999). Hepatitis A superimposed on chronic liver diseases is associated with more severe disease, including fulminant hepatic failure and a higher fatality rate (Vento et al., 1998). Hepatitis A thus poses a particular threat to injecting DUs because the high prevalence of hepatitis C virus (HCV) in this group (Alter, 1999, Trepo and Pradat, 1999). Injection illicit drugs is the most important risk factor for HCV infection in developed countries (Alter et al., 1999).
Commercially available inactivated hepatitis A vaccine has been extensively studied in persons of all ages. The majority of these studies demonstrate nearly a 100% seroconversion rate after a primary vaccination course in both adults and children (CDC, 1999, Van Damme et al., 1994, Clemens et al., 1995, Lemon and Thomas, 1997).
Reports of studies in illicit DUs have shown a low responsiveness to hepatitis B vaccination, (Rumi et al., 1991, Quaglio et al., 2002, Lugoboni et al., 1997) particularly in patients positive for HCV (Rumi et al., 1991, Wiedmann et al., 2000). The immunogenicity of hepatitis A vaccine among DUs, however, has not yet been defined. Only one study to date has evaluated the rate of seroconversion in a cohort of DUs. It showed a much lower seroconversion rate compared to healthy subjects (Lugoboni et al., 2000).
The present study was undertaken to evaluate the safety, immunogenicity and reactogenicity of an inactivated hepatitis A vaccine among DUs, and to assess adherence to the vaccination protocol.
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Research participants
The data presented in this study were collected from January 1, 2002 through December 31, 2002 at three Public Health Centers for Drug Users (PHCDUs) in northern Italy. Eligible participants included injecting and non-injecting heroin users (some of whom were probably users of other illicit drugs). Exclusion criteria were seropositivity for HIV and having received immunosuppressive therapy within 6 months prior to entry into the study. All participants gave written informed consent. No
Results
In the study period 151 subjects were tested for the presence of anti-HAV. Of all, 45 were positive (30%) and 106 were negative. Of this second group, vaccination was proposed to 50 patients and 44 were vaccinated. Five subjects said they were not interested in vaccination and one was admitted to hospital. Vaccination was not put forward to other 56 patients because the time available was insufficient to carry it out with all the necessary post vaccine controls, (due largely to admission to a
Discussion
Inactivated hepatitis A vaccine proved safe when administered to this cohort of DUs, as indicated by the very low incidence of symptoms following vaccination. Furthermore, hepatitis A vaccine induced a satisfactory immune response in DUs as indicated by 100% of subjects being positive for anti-HAV after the full course of vaccination.
Although all DUs proved seropositive after the booster vaccination, the seroconversion rate, at the 2 and 6 month time points was much lower than in healthy
Acknowledgements
The research was supported by internal funds only. We are very thankful to Irene Spilimbergo, MD, Maddalena Sarti, MD, Anna Fornasiero, MD and Carlo Bossi, MD, for collecting data. We are particularly indebted to nurse Annamaria Michielin, from the PHCDU of Castelfranco Veneto (Treviso), for data and blood sample collection.
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