Background Chronic hepatitis B infection is endemic in New Zealand and has high prevalence in New Zealand Māori. Previous longitudinal studies in populations with predominantly vertically acquired chronic hepatitis B have shown low spontaneous hepatitis B surface-antigen (HBsAg) seroclearance rates: 0.5–1.4% annually (mean age of clearance 48 years). We report the 28-year follow-up data on clinical and serological outcomes in indigenous New Zealand Māori with early horizontally acquired HBV.

Methods In 1984, community seroprevalence study identified 572 HBsAg-positive individuals, followed for 28 years. Liver-related mortality and hepatocellular carcinoma (HCC) incidence were compared between these 572 HBV carriers and 1140 HBsAg-negative matched case-controls. Surviving HBsAg-positive individuals have been followed up in 2012 with clinical assessment, blood tests and liver transient elastography. Rates of hepatitis B e-antigen (HBeAg) and HBsAg seroconversion were determined.

Results After total 13 187.4 person-years follow-up, 15 HBsAg-positive patients have developed HCC compared with none of the HBsAg-negative controls (p<0.001). 12 HBsAg-positive patients died from liver-related causes compared with none in the controls (p<0.001). Spontaneous HBeAg-seroconversion occurred in 91% of HBeAg-positive patients. Spontaneous HBsAg loss occurred in 33% overall (annual clearance rate 1.34%), with higher rates at older ages (1.05% in patients<20 years at entry vs 4.3% per annum >40 years at entry, p<0.0001). Median ages of HBeAg loss and HBsAg loss were 23 years (range 6–66 years) and 40 years (range 4–80 years), respectively.

Conclusions Horizontally transmitted HBV in Maori is similarly associated with increased risk of liver-related mortality and HCC compared with Chinese, although absolute incidence rates are lower. The rates of HBeAg and HBsAg loss are high, and occur at an earlier age than previously reported.