Hepatitis B virus immunity prior to and after administration of a 'booster' dose of vaccine among health-care students at a South African university

Abstract

Background: Health-care students (HCSs) are at risk of occupational exposure to hepatitis B virus (HBV) infection despite an effective hepatitis B vaccine (HepB) being available. The majority of current HCSs are born after HepB was introduced into the South African Expanded Programme on Immunisation in 1995. Thus, it is assumed that having received HepB in infancy, a single 'booster' dose would suffice. This study aimed to investigate HBV immunity prior to and after administration of a HepB 'booster' dose.

Methods: Hepatitis B surface antibody (anti-HBs) levels were determined in first year HCSs at the University of the Witwatersrand, before and after receiving the 'booster'. Participant demographics and HepB history were captured using a structured questionnaire.

Results: Before receiving the 'booster', 56% (101/180) had anti-HBs < 10 mIU/mL and were non-immune. A further 35% had anti-HBs levels of 10 - 99 mIU/mL, and 9% had ≥100 mIU/mL. <30% of HCSs self-reported completion of a three-dose primary series, which was significantly associated with higher baseline anti-HBs levels compared to those with a partial schedule (p = 0.045). Following vaccination, 39% (71/180) returned for follow-up with a significant median (IQR) increase of 476 (151 - 966) mIU/mL (p < 0.001). Of the 45 students who had non-immune baseline levels, 73% (33/45) responded with ≥100 mIU/mL, 16% (7/45) with 10 - 99 mIU/mL and 11% (5/45) remained non-immune. Levels of ≥100 mIU/mL were achieved by 100% of students with baseline levels ≥10 mIU/mL (n = 26).

Conclusion: More than half of the HCSs were not immune to HBV prior to receiving the recommended 'booster' vaccine. Following vaccination, 7% (5/71) remained unprotected. This study highlights that in the absence of vaccination records and without confirming the immune status of HCSs, it cannot be assumed that HCSs will be protected following a 'booster'. Policy reform and inclusion of serological tests for immunity prior to HCSs initiating clinical exposure are recommended.

Keywords: Health-care students; HepB; Hepatitis B virus; Immunity; Vaccination.

Fig. 1

Flow diagram of study participants for inclusion in pre-vaccination (N = 180) and post-vaccination (N = 71) data analysis anti-HBs (hepatitis B surface antibody); HBV (hepatitis B virus).

Fig. 2

Hepatitis B immune response following vaccination with a single ‘booster’ dose, grouped according to pre-vaccination (baseline) hepatitis B surface antibody (anti-HBs) immune category. Participants in various categories post vaccination reported as frequency (n) and percentages (%). Non-immune (anti-HBs < 10 mIU/mL), low immunity (anti-HBs 10 − 99mIU/mL), high immunity (≥100 mIU/mL). ^***McNemar’s test for significance (p < 0.001) for paired categorical data.

Fig. 3

Post-vaccination anti-HBs level in comparison with pre-vaccination anti-HBs level (Spearman’s rank correlation (rho) r_s = 0.566, p < 0.001). Shaded area includes 95% confidence interval for linear plot; horizontal dotted line indicates anti-HBs < 10 mIU/mL (below which values are non-reactive) anti-HBs (hepatitis B surface antibody).