# Hepatitis B Virus Genotypes and Subgenotypes Circulating in Infected Residents in a Country with High Vaccination Rate

## TL;DR

This study examines the diversity of hepatitis B virus genotypes in Portugal, where vaccination is widespread, and finds that most infections are linked to immigrants from high-prevalence regions.

## Contribution

The study provides updated insights into HBV genotypes and subgenotypes circulating in Portugal, highlighting the role of immigration in viral diversity.

## Key findings

- HBV subgenotypes A1–A3, D1–D4, E, and F4 were identified in infected residents in Portugal.
- Genotypes E and F, common in Africa and South America, were found in native Portuguese individuals.
- No resistance mutations in the RT sequences were detected among the studied samples.

## Abstract

Despite the availability of a vaccine against hepatitis B virus (HBV), this infection still causes public health problems, particularly in susceptible populations. In Portugal, universal free vaccination started in 1994, and most HBV infections are diagnosed in immigrants from high-prevalence countries. Our aim was to assess the pattern of HBV genotypes/subgenotypes in samples collected between 2017 and 2021 from a convenience sample of 70 infected residents in Portugal. The HBV pol/HBsAg region was amplified and sequenced, allowing the analysis of RT sequences submitted to phylogenetic analysis and mutations assessment. A total of 37.1% of samples were from native Portuguese, aged 25–53 years (mean: 36.7 years), and the remaining samples were from individuals born outside of Portugal. A high diversity of HBV was identified: subgenotypes A1–A3 in 41.0% (16/39); D1, D3, and D4 in 30.7% (12/39); E in 23.1% (9/39); and F4 in 2.6% (1/39). Besides genotypes A and D, Portuguese were also infected with genotypes E and F, which are prevalent in Africa and South America, respectively. Resistance mutations in RT sequences were not found. The findings provide valuable insights for updating the HBV molecular epidemiology in Portugal. However, successful strategies to prevent and control the infection are still needed in the country, especially among susceptible and vulnerable populations.