EVOLVE-HBV: A retrospective cross-sectional study to quantify and characterise HBV infection, exposure, immunity and susceptibility in a rural population in KwaZulu-Natal, South Africa

This retrospective cross-sectional study in rural KwaZulu-Natal, South Africa, reveals a high prevalence of Hepatitis B Virus infection (10.4%) and exposure (34.9%) alongside low vaccine-mediated immunity, underscoring an urgent need for scaled-up interventions to meet global elimination targets.

The Gist

Imagine a village in rural South Africa as a large, bustling neighborhood. For years, the health officials have been worried about a silent intruder called Hepatitis B (HBV). This virus is like a stealthy burglar that can sneak into a person's liver, hide there for years, and eventually cause serious damage like a house burning down slowly over time.

The study you're asking about, called "EVOLVE-HBV," is like a massive, neighborhood-wide "health check-up" to answer three big questions:

1. How many people have the burglar inside them right now? (Infection)
2. How many people have already kicked the burglar out but remember the fight? (Past exposure/immunity)
3. How many people have a "security system" (vaccine) that stops the burglar from entering? (Vaccine immunity)

Here is the story of what they found, told in simple terms.

1. The Neighborhood Check-Up

The researchers didn't just guess; they went into the archives of a previous health program called "Vukuzazi" (which means "Wake Up" in Zulu). They pulled out blood samples from 2,200 people. To make sure the results represented the whole town and not just a specific group, they used a special mathematical "scale" (weights) to balance the numbers, much like ensuring a survey includes people of all ages, genders, and backgrounds.

2. The Big Findings: A Mixed Bag

The "Burglar" is Still Hiding (High Infection)
They found that about 1 in 10 people (10.4%) currently have the Hepatitis B virus active in their bodies. That's a lot higher than the global goal for elimination.

• The Twist: The virus isn't spread evenly. It's like a patch of weeds in a garden; it's much thicker in the southern, semi-urban parts of the region (near the highway) and thinner in the deep rural north.

The "Scarred" Veterans (Past Exposure)
About 35% of the people had fought the virus in the past and cleared it. Their immune systems won the battle, but they don't have the "vaccine shield" anymore. They are safe from getting infected again, but they carry the memory of the fight.

The "Empty Shields" (Low Vaccine Success)
This is the most worrying part. Only about 9% of the whole population had immunity from the vaccine.

• The Good News: For the youngest generation (born after 2000, when the vaccine became common), the number jumped to 20%. It's like seeing new houses in the neighborhood finally getting strong security systems.
• The Bad News: For everyone else, the vaccine coverage is very low. Most people are walking around with "open doors," making them susceptible (vulnerable) to catching the virus.

3. Who is Most at Risk?

The study looked at who was more likely to have the virus or be vulnerable:

• HIV Connection: People living with HIV were more likely to have been exposed to Hepatitis B. It's like having a weak front door (HIV) makes it easier for the burglar (HBV) to get in.
• Gender Surprise: Usually, men get Hepatitis B more often in other parts of the world. Here, men and women were almost equally affected. This suggests women in this specific area might be just as vulnerable as men, which is a new clue for doctors.
• Lifestyle: Interestingly, drinking alcohol was linked to lower vaccine immunity. It's as if alcohol was rusting the security system, making the vaccine less effective.

4. The Treatment Problem: Who Gets the Keys?

The researchers asked: "If we had the keys to the cure (antiviral drugs), who would qualify to get them?"

• The Old Rules: In the past, only people with very sick livers got the keys.
• The New Rules (2024): The World Health Organization recently said, "Let's be more generous. If you have the virus, you should probably get the keys to stop it from getting worse."
• The Result: Under these new, more helpful rules, over 60% of the people with the virus would qualify for treatment. However, right now, most of them aren't getting it. They are stuck in a waiting room because the healthcare system doesn't have a clear path to give them the medicine.

5. The Takeaway: Why This Matters

Think of the Hepatitis B virus as a slow-moving fire.

• The Fire is Spreading: Because so many people are susceptible (no vaccine) and so many are infected, the fire is still burning in this community.
• The Extinguisher is Available: We have the vaccine (to stop new fires) and the medicine (to put out existing fires).
• The Problem: The hose isn't reaching everyone. The study shows that while the vaccine program started in the 90s, it hasn't reached everyone effectively, and the treatment system is broken for those who need it.

In a nutshell: This study is a wake-up call. It tells us that in rural KwaZulu-Natal, Hepatitis B is still a major threat. We need to fix the "security systems" (vaccines) for the young and middle-aged, and we need to open the "medicine cabinet" (treatment) for the majority of infected people who are currently waiting for help. If we don't act, the "house" (the community's liver health) could face a much bigger disaster in the future.

Technical Summary

1. Problem Statement

Despite global targets to eliminate Hepatitis B Virus (HBV) as a public health threat by 2030, data regarding HBV epidemiology in African populations remain scarce. In South Africa (SA), estimates of the prevalence of people living with HBV (PLWHB) vary widely (1.9 to 3.5 million), and the region is classified as middle-to-high prevalence.

• The Gap: There is a lack of systematic screening pathways for HBV in SA, and existing data often fail to account for the complex interplay between HBV, HIV, and non-communicable diseases (NCDs) in a "syndemic" context.
• The Challenge: Determining accurate prevalence is complicated by assay performance variability in African populations, the high rate of HIV co-infection (which affects HBV viraemia and treatment), and the recent shift in WHO guidelines toward more inclusive treatment eligibility criteria.

2. Methodology

Study Design:
A retrospective, cross-sectional study nested within the Vukuzazi community health programme in rural uMkhanyakude, KwaZulu-Natal (KZN), South Africa.

Population & Sampling:

• Cohort: 2,200 archived plasma samples collected between May 2018 and March 2020 from participants aged ≥15 years.
• Stratification: Samples were stratified by birth cohort (to reflect vaccination eras), sex, and HIV status:
  • Pre-vaccine (born <1995)
  • Peri-vaccine (born 1995–1999)
  • Post-vaccine (born 2000–2005)
• Weighting: Statistical weights were applied to account for unequal selection probabilities and non-response, ensuring estimates were generalizable to the surveillance population.

Laboratory Testing:

• Primary Markers: HBsAg (surface antigen), anti-HBc (core antibody), and anti-HBs (surface antibody).
• Secondary Markers (for HBsAg+): HBeAg, Alanine Aminotransferase (ALT), and HBV DNA viral load (VL).
• Assay: Primary screening used the Abbott platform (HBsAg S/CO >1.0). Sensitivity analyses were performed using stricter cut-offs (S/CO >10).
• Classification: Participants were categorized into four groups:
  1. Infection: HBsAg positive.
  2. Exposure/Clearance: HBsAg negative, anti-HBc positive.
  3. Vaccine-mediated Immunity: Anti-HBs positive only.
  4. Susceptible: Negative for all markers.

Treatment Eligibility:
Eligibility was assessed using 2024 WHO guidelines, considering HBV DNA >2,000 IU/mL, ALT elevation, and comorbidities (HIV, diabetes).

3. Key Contributions

• First Population-Based Data: Provides the first robust, weighted prevalence estimates of HBV infection, exposure, and immunity in a rural South African setting.
• Syndemic Analysis: Investigates the intersection of HBV with HIV and metabolic NCDs (diabetes, hypertension, obesity) in a high-burden setting.
• Diagnostic Validation: Highlights the challenges of HBsAg assays in African populations, noting discrepancies between HBsAg and anti-HBc positivity rates that suggest potential false positives or occult infections.
• Treatment Gap Quantification: Quantifies the proportion of the population eligible for treatment under new, simplified WHO guidelines versus current access.

4. Key Results

Prevalence Estimates (Weighted):

• Active HBV Infection: 10.4% (95% CI: 9.0–12.1%).
• Exposure with Clearance: 34.9% (95% CI: 32.4–37.5%).
• Vaccine-Mediated Immunity: 8.9% overall. However, this rose to 20.2% in the post-vaccine cohort (born 2000–2005), indicating partial success of the infant immunization program but still far below WHO targets.
• Susceptibility: 45.8% of the population is susceptible to HBV infection.

Demographic & Clinical Correlates:

• HIV Co-infection: PLWH had higher rates of HBV exposure/clearance (39.2% vs. 27.3% in HIV-negative) but lower vaccine-mediated immunity.
• Birth Cohorts: Infection prevalence decreased in younger cohorts (11.8% in pre-1995 vs. 6.6% in 2000–2005), though this was not statistically significant after adjustment.
• Geography: Spatial mapping revealed heterogeneity, with the highest infection rates in the south/south-eastern peri-urban areas (bordering a national highway) and lowest in the rural north-west.
• Risk Factors:
  • Alcohol: Associated with lower vaccine-mediated immunity.
  • SES/Education: Higher socioeconomic status was associated with lower susceptibility and higher clearance rates.
  • Sex: No significant difference in infection prevalence between males and females (unlike global trends where males are often higher risk).

Treatment Eligibility:

• Using the relaxed diagnostic threshold (HBsAg S/CO >1), >60% of individuals with active HBV met the criteria for treatment under 2024 WHO guidelines (driven largely by HIV co-infection and comorbidities).
• Currently, treatment is largely limited to those on HIV ART; those with HBV monoinfection have limited access to specific HBV therapy.

5. Significance and Implications

• High Burden, Low Immunity: The study confirms that HBV remains endemic in rural KZN with high infection rates and critically low vaccine-induced immunity, leaving nearly half the population susceptible.
• Urgent Need for Scale-Up: The finding that >60% of infected individuals qualify for treatment under new guidelines underscores an immediate need to expand access to antivirals (specifically Tenofovir, which treats both HIV and HBV) and diagnostic testing.
• Syndemic Approach: The data supports integrating HBV management into existing HIV and NCD care pathways (decentralized services) to improve efficiency and reach rural populations.
• Diagnostic Caution: The study highlights the need for better validation of HBsAg assays in African settings, as the discordance between HBsAg and anti-HBc results suggests potential over-diagnosis or complex immunological profiles (e.g., occult HBV) that current screening may miss or misclassify.
• Policy Impact: The results advocate for strengthening birth-dose vaccination programs and implementing the 2024 WHO simplified treatment criteria to accelerate progress toward the 2030 elimination goals.