Hepatitis a virus infection in Central-West Tunisia: an age structured model of transmission and vaccination impact

Abstract

Background: The epidemiological pattern of hepatitis A infection has shown dynamic changes in many parts of the world due to improved socioeconomic conditions and the accumulation of seronegative subjects, which leads to possible outbreaks and increased morbidity rate. In Tunisia, the epidemiological status of hepatits A virus is currently unknown. However, over the past years higher numbers of symptomatic hepatitis A virus infection in school attendants and several outbreaks were reported to the Ministry of Health, especially from regions with the lowest socioeconomic levels in the country. The aim of this study was to investigate the current seroprevalence of hepatitis A virus antibodies in central-west Tunisia and assess the impact of hepatitis A virus vaccination on hepatitis A epidemiology. Methods: Serum samples from 1379 individuals, aged 5-75 years, were screened for hepatitis A virus antibodies. Adjusted seroprevalence, incidence and force of infection parameters were estimated by a linear age structured SEIR (Susceptible-Exposed-Infectious-Recovered) compartmental model. A vaccine model was then constructed to assess the impact on hepatitis A virus epidemiology of 3 scenarios of vaccination strategies: one dose at 12-months of age, one dose at 6-years and one dose at 12-months and another at 6-years of age during 6 years. Results: A rapid increase in anti-hepatitis A virus seroprevalence was noted during infancy and adolescence: 47% of subjects under 10-years-old are infected; the prevalence increases to 77% at 15-years and reaches 97% in subjects aged 30-years. The force of infection is highest between 10 and 30-years of age and the incidence declines with increasing age. The vaccine model showed that the 3-scenarios lead to a significant reduction of the fraction of susceptibles. The two doses scenario gives the best results. Single-dose vaccination at 6-years of age provides more rapid decrease of disease burden in school-aged children, as compared to single-dose vaccination at 12-months, but keeps with a non-negligible fraction of susceptibles among children < 6-years.

Seroprevalence of hepatitis A virus infection in Central‐West of Tunisia

“…To identify the most promising approach, the seroprevalence results of this study were employed to investigate the impact of different HAV vaccine strategies introduction on the HAV epidemiology in Central‐West of Tunisia. The study conducted evaluated the currently targeted vaccination strategy compared with others potential vaccination strategies 60 . It showed that implementation of HAV vaccine lead to a significant reduction in morbidity and mortality rates with best result when HAV vaccine is introduced for those aged 1 and 6 years 60 .…”

“…The study conducted evaluated the currently targeted vaccination strategy compared with others potential vaccination strategies 60 . It showed that implementation of HAV vaccine lead to a significant reduction in morbidity and mortality rates with best result when HAV vaccine is introduced for those aged 1 and 6 years 60 . However, additional studies should be conducted to better evaluate the currently targeted vaccination strategy and the others potential vaccination strategies and their cost‐effectiveness.…”

Trends in Adult and Elderly Vaccination: Focus on Vaccination Practices in Tunisia and Morocco

“…The World Health Organization (WHO) estimated that in 2016, 7,134 patients died from hepatitis A worldwide, with most cases in LMIC (20). In many African countries including Tunisia, prevalence of hepatitis A has decreased with the improvement of sanitary and socioeconomic conditions; they have transitioned from high endemicity to low (64). In Morocco, 222 cases of hepatitis A were reported in 2015 (65).…”

Modeling the Transmission Dynamics of Hepatitis A with Combined Vaccination and Sanitation Mitigation

“…Recently, scholars such as in [ 16 , 17 ] have also studied the dynamics and the effects of a vaccination strategy in containing HA infection. In particular, [ 16 ] developed a mathematical model of HAV transmission to assess trends of regional spread and the effect of vaccination on the extent and timing of the HAV outbreak in Michigan.…”

“…Specifically, they evaluated the proportion of cases prevented by the vaccination program in Southeast Michigan and the remainder of the state. However, [ 17 ] established a linear age-structured SEIAR (susceptible-exposed-symptomatic-asymptomatic-recovered) compartmental model to examine the dynamics and effects of various vaccination approaches on HAV evolution.…”