Published in PLOS One on 2026-02-26, this study is presented as an attributed evidence briefing. The excerpts below are the original researchers’ words, reproduced under their Creative Commons Attribution licence. Health Signal has selected the abstract and, where needed, opening background paragraphs; the complete methods, results, limitations and references remain in the linked paper.
Original authors: Enock Syabbalo, Sydney Mpisa, Michael J. Vinikoor, Mercy Wamundila, Likando Munalula, Taonga Musonda, Ruth Phiri, Paul Kelly, Chloe Thio, David L. Thomas, Edford Sinkala
Source: PLOS One • DOI 10.1371/journal.pone.0339690
Read the complete primary study ↗ · Creative Commons Attribution licence
From the researchers
Abstract
Because of its low cost and lasting effects, hepatitis B virus (HBV) vaccination of adults in Africa could significantly contribute to viral elimination. Among at-risk adult populations there are few data to inform vaccine implementation, including on pre-existing immunity and vaccine uptake. We serologically profiled adults with specific risk factors for HBV infection in urban Zambia and evaluated their uptake of vaccine.
At a tertiary hospital in Lusaka, we recruited hepatitis B surface antigen-negative adult (age 18+) contacts to people with chronic HBV, health workers (HCWs), and people with HIV (PLWH). After we jointly collected blood and gave the first HBV vaccine dose (blind to the full serological profile), we called back those whose results showed insufficient surface antibodies (anti-HBs) to complete the 3-dose series at 1 and 6 months, and we reimbursed transport costs. Stratified by group, we described the proportions of participants with past vaccination, resolved infection (anti-HBc-positive regardless of anti-Hbs status), isolated core antibodies (anti-HBc-positive and anti-HBs-negative), and neither antibody. We described the correlates of resolved infection. We described completion of the vaccine series in anti-HBs-negatives. In those with isolated core antibodies, we explored the incidence of an anamnestic response based on post-first-dose anti-HBs > 10 IU/ml and>= 1-log increase from baseline.
616 adults (median age, 32.2 years, IQR [26.7–43.8]; 61.2% women) enrolled, including 333 contacts, 213 HCWs, and 70 PLWH. Half had neither antibody, including 68.5% of health workers. Prior vaccination was seen in 8.3% overall, including 11.3% of HCWs. Resolved infection was present for 39.3% and was more prevalent with increased age and among contacts. Isolated core was present in 59 (9.6% overall and 24.7% of those with resolved infection) participants. Among the 383 participants eligible for vaccination, 377 (98.4%) received 1 dose, 190 (49.6%) received 2 doses, and 54 (14.1%) completed the series. Among 18 individuals with isolated core antibodies, none had detectable HBV DNA, and 9 (50%) had an anamnestic response.
Most adults at risk for HBV in Lusaka, Zambia, had inadequate immunity, which could undermine HBV elimination. High resolved infection rate in contacts supports the role of index testing in HBV case finding. Low vaccine completion, despite vaccine access and addressing transportation costs, was striking and underscores the need for integrated behavioral science approaches to improve implementation of this potentially cost-effective intervention. Low rates of anamnestic response in people with anti-HBc-positivity should be further studied in Africa.
Introduction
With 1.2 million new infections annually [1], 300 million people chronically infected [2] and 2 billion people having been previously infected, Hepatitis B continues to be an infectious disease of public health importance globally. Viral hepatitis for which Hepatitis B forms the majority of the infections, was the 2nd leading cause of death amongst infectious diseases in 2022, behind COVID 19 [1]. Hepatitis B infection mortality is mainly due to liver cirrhosis and/or hepatocellular carcinoma. Africa is disproportionately affected by Hepatitis B, accounting for 80 million chronic cases [3] and most new global infections [4]. To reduce new infections, infant vaccination, including at birth, is a major strategy for hepatitis B elimination since infection early in life is less likely to naturally resolve than in adulthood.
Reading this evidence
Use the full paper to check the study design, participant selection, comparator and outcome definitions before drawing a practical conclusion. An association does not by itself show cause and effect. A reported performance measure needs its denominator and uncertainty. A finding from a particular facility, sample or time period should retain that scope when it is discussed elsewhere.
This briefing makes the source accessible within the wider financing & policy desk. It does not assess an individual patient or certify a product. When considering relevance to another health system, examine the original authors’ account of context and limitations, then seek local implementation evidence. The related reporting below provides other studies to read alongside this one; it is a topic connection, rather than a claim that their results are directly comparable.
© 2026 Enock Syabbalo, Sydney Mpisa, Michael J. Vinikoor, Mercy Wamundila, Likando Munalula, Taonga Musonda, Ruth Phiri, Paul Kelly, Chloe Thio, David L. Thomas, Edford Sinkala. Excerpts reproduced under CC BY. Selection, formatting and contextual notes by Health Signal. The researchers are the authors of the source study, not members of Health Signal’s staff.
Explore connected evidence
- Evidence brief: Impact of demographic factors and HIV status on Hepatitis B vaccination adherence and completion rate among high-risk populations in Lagos State, Nigeria
- Evidence brief: Hepatitis B vaccine uptake and associated factors among pregnant women attending antenatal care at Gulu Regional Referral Hospital, Northern Uganda
- Evidence brief: Towards hepatitis B elimination in Ghana: vaccination coverage and its predictors among informal sector workers in Kejetia, Kumasi, Ghana
