Susceptibility to Hepatitis A and B Virus Among Clients at a Syringe Services Program in Philadelphia, 2018

Although many people who use drugs meet criteria for vaccination against hepatitis A virus (HAV) and hepatitis B virus (HBV), estimates of susceptibility (ie, lack of immunity) are not well established. This study sought to identify the prevalence of and characteristics associated with HAV and HBV susceptibility among people who use drugs attending an urban syringe services program.

We initiated this seroprevalence study in 2018 among 438 clients of a syringe services program who met study criteria, including provision of a blood specimen and a self-reported history of drug use. We assessed HAV and HBV susceptibility and infection via serological testing. We examined associations between participant characteristics and serology status by using descriptive statistics and multivariable logistic regression models.

Of the initial 438 clients identified, 353 (80.6%) met study criteria. Of 352 participants with conclusive HAV test results, 48.6% (n = 171) were HAV susceptible; of 337 participants with conclusive HBV test results, 32.6% (n = 110) were HBV susceptible, 24.3% (n = 82) showed evidence of past or present HBV infection, and 43.0% (n = 145) had vaccine-derived immunity. Compared with participants born before 1970, participants born during 1980-1989 had 5.90 (95% CI, 2.42-14.40) times the odds of HAV susceptibility and 0.18 (95% CI, 0.06-0.53) times the odds of HBV susceptibility, and participants born during 1990-1999 had 6.31 (95% CI, 2.34-17.00) times the odds of HAV susceptibility. Decreased odds of HAV susceptibility were associated with homelessness (adjusted odds ratio = 0.48; 95% CI, 0.28-0.82).

Despite applicable HAV and HBV vaccination recommendations, substantial gaps exist in HAV and HBV susceptibility among a population of people who use drugs. These findings highlight the need for increased HAV and HBV vaccination efforts among people who use drugs.