Viruses 20146(3), 1336-1345;

Hepatitis A immunity in the District of Aveiro (Portugal): an eleven-year surveillance study (2002-2012)

Sara Pereira1, Inês Linhares1, António Ferreira Neves2, Adelaide Almeida1*

1    Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal;

2     Clinical Analysis Laboratory Avelab, Rua Cerâmica do Vouga, 3800-011 Aveiro, Portugal;

* Corresponding author Email:



Hepatitis A is a common viral liver disease and brings serious health and economic problems as its epidemiologic pattern changes over time. National serosurveys from developed countries have indicated a decline in HAV (hepatitis A virus) seroprevalence over time due to the improvement of economic and sanitation levels. The hepatitis A virus (HAV) immunity rate was surveyed throughout an eleven-year period by sex and age group in Aveiro District. In this retrospective study, blood samples from patients of Aveiro District, in ambulatory regime, collected at the Clinical Analysis Laboratory Avelab between 2002 and 2012 were screened for the presence of antibodies against HAV antigen using a chemiluminescence immunoassay. The global immunity (positive total anti-HAV) was 60% and only 0.3% of the patients presented recent infection by HAV (positive IgM anti-HAV). The HAV immunity was age-dependent (p < 0.05), but no significant differences (p > 0.05) between sexes were observed. The immunity was similar throughout the study period (p > 0.05). The results of this study indicate that young people (especially under 25 years old) from District of Aveiro are susceptible to HAV infection, constituting a high risk group. The elderly should be also a concern in the future of Hepatitis A infection.



Hepatitis A is an acute disease transmitted by fecal-oral route, either by direct contact with an HAV-infected person or by ingestion of HAV-contaminated food or water. The main serological marker, IgM anti-HAV can be detected between five days and 6 months after exposure. Anti-HAV IgG confers lifelong immunity and this antibody can also be detectable in the symptomatic phase [2,3].

In developed countries, the HAV (hepatitis A virus) incidence has declined essentially due to the great improvements of sanitary conditions [4]. However, a decrease of immune individuals leads to an increased risk of potential outbreaks. In such circumstances, these outbreaks may be unpredictable and difficult to control. This concern is also focused on the fact that, in children, hepatitis A is mostly asymptomatic. In adults, 70-89% of cases are symptomatic and with increasing age the symptoms are worsened. [5]

In 2011, the WHO has compiled the immunity studies made across the world and a summary was made. In western countries, the overall immunity was 50%, and less than 20% to people aged less than 20 years, suggesting a decline in HAV seropravalence over time [6].

This study aims to evaluate the prevalence of hepatitis A in Aveiro District, from 2002 to 2012, in order to broaden knowledge on the epidemiology of this disease in Portugal and to assess the risk of outbreaks of HAV.

We first analysed all serum samples for total anti-HAV and IgM anti-HAV (using a chemiluminescent label) from patients of Aveiro District in ambulatory regime, collected at the Clinical Analysis Laboratory Avelab (Aveiro, Portugal) during the period 2002–2012.

The samples were classified as immune and non-immune, according to the detected antibodies. The patients were classified as immune when the result of total anti-HAV was positive. Patients with negative anti-HAV antibodies (total anti-HAV negative and IgM anti-HAV negative) were considered non-immune.

Throughout the study period, slight changes in the incidence of the overall immunity were observed, but considering only the results of total anti-HAV the percentage of immunity did not vary significantly (p>0.05) (Fig. 1).

The overall immunity was not significantly different between female and male patients (p>0.05). However, significant differences in seroprevalence among the different age groups were observed (p<0.05). The age of the immune patients ranged from 0 to 99 years old with a mean age of 42 years old. With the exception of patients aged less than 5 years, there was an overall increase of immunity with age. A gradually increase (54.8%) of immunity in patients with age comprised between 6 -15 years and between 56-65 years was observed, in spite of a decrease of immunity of about 5% in patients aged between 56-65 and with more than 66 years. For patients aged over 25 years, the percentage of immunity was higher than 50% (Fig. 2).






Having into account both currently used analyses (IgM anti-HAV and total anti-HAV), the percentage of immunity decreased during the study period but this decrease was result of a change in the type of analysis required by the patients. Considering only total anti-HAV detection to evaluate the immunity, no significant changes were found during the study period.

In this study, in the Aveiro District, the immunity rate was 22.1% for patients aged 6 to 15 years and 37.2% for patients aged 16 to 25 years. There was a great decrease in prevalence of anti-HAV antibodies throughout the last years for these age groups. The decrease in the immunity rate for the young patients can be explained by the improvement of sanitary conditions.

Although the rate of immunity increased with age, for the children groups it was quite low, under 25%, which could lead to an increased risk of unpredictable outbreaks in the future. For the elderly people (>66) the immunity was lower than that observed for people aged 55 to 66 years old, what can be explained by the gradual weakening of the immune system with age.

Importance of the study: The decrease in the immunity in older patients, associated to the increase in the mortality rate in people over 50 years old, suggests that the impact of future infections will be also a concern for the elderly group. In the future, cost effectiveness studies of hepatitis A vaccine will be important to the decision of introducing universal vaccination of the Portuguese population, taking in account that some reports have shown its value in other developed countries.



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