Determinants of hepatitis A vaccine immunity in a cohort of human immunodeficiency virus-infected children living in Switzerland

Abstract

Vaccination in HIV-infected children is often less effective than in healthy children. The goal of this study was to assess vaccine responses to hepatitis A virus (HAV) in HIV-infected children. Children of the Swiss Mother and Child HIV Cohort Study (MoCHiV) were enrolled prospectively. Recommendations for initial, catch-up, and additional HAV immunizations were based upon baseline antibody concentrations and vaccine history. HAV IgG was assessed by enzyme-linked immunosorbent assay (ELISA) with a protective cutoff value defined as ≥10 mIU/ml. Eighty-seven patients were included (median age, 11 years; range, 3.4 to 21.2 years). Forty-two patients were seropositive (48.3%) for HAV. Among 45 (51.7%) seronegative patients, 36 had not received any HAV vaccine dose and were considered naïve. Vaccine responses were assessed after the first dose in 29/35 naïve patients and after the second dose in 33/39 children (25 initially naïve patients, 4 seronegative patients, and 4 seropositive patients that had already received 1 dose of vaccine). Seroconversion was 86% after 1 dose and 97% after 2 doses, with a geometric mean concentration of 962 mIU/ml after the second dose. A baseline CD4(+) T cell count below 750 cells/μl significantly reduced the post-2nd-dose response (P = 0.005). Despite a high rate of seroconversion, patients with CD4(+) T cell counts of <750/μl had lower anti-HAV antibody concentrations. This may translate into a shorter protection time. Hence, monitoring humoral immunity may be necessary to provide supplementary doses as needed.

Fig 1

Study population. Unimmunized, no previous HAV immunization; Primed, one previous dose of HAV vaccine; Fully immunized, ≥2 previous doses of HAV vaccine.

Fig 2

Anti-HAV antibody concentrations after the first (priming) and second (boosting) HAV vaccinations.

Fig 3

Serum antibody concentrations according to CD4⁺ T cell count after the second HAV vaccine dose. Individual results are displayed as reverse cumulative distribution curves.

Fig 4

Correlation of antibody concentrations after the first (priming) and second (boosting) vaccine doses. Solid line, linear correlation fit line; Pc, Pearson coefficient; dashed line, separation between patients (8/23) with a ≥1.5-log increase in antibody concentration between the first (priming) and second (boosting) doses.