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Background: Hepatitis A (HAV) is common in HIV⁺ patients.  Superinfection with HAV in patients with chronic hepatitis C (HCV) can lead to fulminate hepatic failure. The USPHS/IDSA guidelines for Prevention Of Opportunistic Infections In Persons with HIV recommends that all susceptible HIV patients at increased risk for HAV or with chronic liver disease, be vaccinated against HAV.  Immune response to HAV vaccine has not been well studied in HIV positive patients. Our goal is to assess  the immune response to HAV vaccination in HIV⁺ patients, and the effect of HIV viral load, CD4 count nadir, and CD4 count at vaccination and antiretroviral use (ART) on immune response rates to HAV vaccination in HIV⁺ patients.

Methods:  Retrospective analysis of all HIV positive patients  seen at HSR and CVAMC between 1/1/2001 and 9/30/2003 who were tested for HAV antibodies.  Patients with negative HAV antibody received 2 HAV vaccines (HAVRIX) 6 to 12 months apart.  Post HAV antibody response was measured after the second vaccine.  Univariate and multivariate analysis was done to determine predictors of response to vaccine.

Results:  Of 485 patients evaluated, 207 had a positive prevaccine HAV antibody result.  Of the 278 included, 103 patients have completed their HAV vaccination series and have post vaccine HAV antibody results.   Of 103 (49%) patients, 51 had positive post vaccine HAV antibody results (responders).  There was no difference in age, race, HIV risk group, ART use, or HCV exposure between vaccine responders and nonresponders;  50% of responders had CD4 nadir <200 compared with 62% of nonresponders (p = 0.25).  The mean nadir CD4 count was lower in nonresponders compared with responders, but this did not reach statistical significance.  In univariate analysis vaccine responders were more likely to be female (40% vs 13.5%, p = 0.001), have a higher CD4 count at vaccine (491 cells/mm³ vs 361 cells/mm³, p = 0.03) and lower viral load at vaccine (5,770 copies/mL vs 29,058 copies/mL, p = 0.02).  Responders were less likely to have a CD4 count <200 cells/mm³ at vaccine compared with nonresponders (14% vs 35%, p = 0.02). Multivariate analysis showed that female sex and higher CD4 count at vaccine were independent predictors of response to vaccine.

Conclusions: Of our HIV⁺ patients, 49% responded to HAV vaccine.  This is much lower than reported rates of 100% in HIV^- patients.  Female sex and CD4 count at vaccine but not CD4 nadir predicted response to vaccine.

Keywords: Hepatitis A; Vaccine; Immune response