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Hepatitis A incidence in Portugal declined from 20.1 to 0.4/100,000 population between 1987 and 2023, changing non-vaccinated population susceptibility. This shift has contributed to more frequent outbreaks, including in 2024-25, highlighting the need to enhance surveillance and integrate serological data.
We aimed to describe the exposure profile of the Portuguese population to hepatitis A virus (HAV) over time by estimating and comparing the seroprevalence of hepatitis A in two nationwide surveys. Data from two cross-sectional seroprevalence studies performed in 2001-02 and 2015-16 in the population aged ≥ 2 years were analysed. Seroprevalence was weighted for population distribution by age, sex and region, and then analysed by birth cohort (1911 -2014) and compared using Poisson regression. Overall prevalence of anti-HAV IgG antibodies was 67.3% (95% CI: 64.2-70.3) in 2001-02 (n = 1,642) and 56.3% (95% CI: 52.4-60.2) in 2015-16 (n = 2,052), showing an 11-percentage-point decline. Birth cohort analysis revealed consistent seroprevalence within each cohort in both surveys, i.e. seroprevalence for the 1981-90 birth cohort was 16.7% and 18.7%, respectively, suggesting that higher seroprevalence is more closely associated with birth cohort (cohort effect) rather than a specific time point. Additionally, we found that individuals aged ≥ 30 years, born before the 1980s, and those with lower education had higher seroprevalence. The immunological profile of anti-HAV antibodies in the Portuguese population has shifted over the last decades. High susceptibility and shifting age distribution of Hepatitis A-seropositive individuals highlight the need to revise future vaccination strategies in Portugal.
Key public health message: - What did you want to address in this study and why? Hepatitis A is an acute liver infection caused by hepatitis A virus (HAV) and transmitted primarily via the faecal–oral route, often through contaminated food or water. Portugal’s socioeconomic and hygiene improvements in the 1980s led to a reduction in HAV circulation and a decline in hepatitis A infections. However, this increased population susceptibility to infection. To measure immunity, we compared seroprevalence of HAV in the population and analysed changes over time. - What have we learnt from this study? We found differences in HAV antibody prevalence between two population studies (2001–02 and 2015–16), mainly depending on individual’s birth year and their prior exposure to the virus. Specifically, we found that individuals aged < 30 years, as well as those born after the 1980s, were associated with lower HAV antibody prevalence. This indicates that more individuals are now susceptible to hepatitis A and that HAV is more likely to affect a wide range of age groups. - What are the implications of your findings for public health? Unlike previous studies focusing on specific regions and/or groups, this study provides a nationwide overview of HAV immunity trends in the Portuguese population over time. Our study highlights that adapting vaccination strategies is important as more individuals become susceptible to hepatitis A. Thus, broad and early childhood vaccination can effectively reduce the spread of HAV.
Key public health message: - What did you want to address in this study and why? Hepatitis A is an acute liver infection caused by hepatitis A virus (HAV) and transmitted primarily via the faecal–oral route, often through contaminated food or water. Portugal’s socioeconomic and hygiene improvements in the 1980s led to a reduction in HAV circulation and a decline in hepatitis A infections. However, this increased population susceptibility to infection. To measure immunity, we compared seroprevalence of HAV in the population and analysed changes over time. - What have we learnt from this study? We found differences in HAV antibody prevalence between two population studies (2001–02 and 2015–16), mainly depending on individual’s birth year and their prior exposure to the virus. Specifically, we found that individuals aged < 30 years, as well as those born after the 1980s, were associated with lower HAV antibody prevalence. This indicates that more individuals are now susceptible to hepatitis A and that HAV is more likely to affect a wide range of age groups. - What are the implications of your findings for public health? Unlike previous studies focusing on specific regions and/or groups, this study provides a nationwide overview of HAV immunity trends in the Portuguese population over time. Our study highlights that adapting vaccination strategies is important as more individuals become susceptible to hepatitis A. Thus, broad and early childhood vaccination can effectively reduce the spread of HAV.
Descrição
Palavras-chave
Hepatitis A Antibodies Cohort Effect Seroprevalence Portugal Determinantes da Saúde e da Doença
Contexto Educativo
Citação
Euro Surveill. 2025 Sep;30(37):2500020. doi: 10.2807/1560-7917.ES.2025.30.37.2500020
Editora
European Centre for Disease Prevention and Control