Serosurveillance of hepatitis A in a region which adopted the universal mass vaccination

Abstract

Hepatitis A is a common infectious disease worldwide that was endemic in many regions of Southern Italy, such as Apulia region. After a large hepatitis A outbreak occurred between 1996 and 1997, in Apulia an active-free immunization program that was targeted to new-borns and adolescents was started. The aim of this study is to investigate the hepatitis A seroprevalence in the adult Apulian population 18 years after the immunization program introduction, in order to evaluate the risk of new epidemics onset.The study was carried out from May 2011 to June 2012 among blood donors from Department of Transfusion Medicine and Blood Bank of Policlinico General Hospital in Bari. Participants signed a written consent and filled out a questionnaire including items on demographic characteristics, risk factors, disease memory, and raw food consumption. Serum samples, collected from each patient, were tested for anti-HAV using the chemiluminescent microparticle immunoassay. Vaccination status against hepatitis A was checked on Regional Digital Immunization Registry (GIAVA).In total 1827 donors agreed to participate (77.7% male) with a mean age of 38.4 ± 11.7 years. However, 1172 (64.1%) donors were seropositive with no difference by sex. The highest proportion of seronegative subjects was in the 27 to 35 years age group. 91.8% of 1-dose vaccinated subjects (n = 190/207; 95%CI = 87.2–95.1) and 96.1% (n = 171/178; 95%CI = 92.1–98.1) of 2-doses vaccinated subjects were immune to the disease. Sensitivity of disease memory in unvaccinated subjects was 14.4% (95%CI = 12.2–16.7), specificity was 97.8% (95%CI = 96.3–98.8), positive predictive value was 91% (95%CI = 85.3–95), and negative predictive value was 42.6% (95%CI = 40–45.2). Raw seafood consumption in unvaccinated subjects was associated with the anti-HAV IgG positivity (OR = 2.1; 95%CI = 1.7–2.7; z = 7.4; P < 0.0001).The vaccination program seems to have changed the virus circulation pattern, with a higher seronegativity rate among subjects not included in the vaccination strategy: 67% of susceptible subjects were among younger people aged 27 to 35 years. Immunization program implementation with a catch-up strategy may be needed to avoid a possible increase of hepatitis A incidence and outbreaks in Apulia. Epidemiological surveillance should be continued and vaccination should actively be offer for free to all the cases contacts, in order to prevent new outbreaks onset.

Changes in seroprevalence of hepatitis A after the implementation of universal childhood vaccination in Shandong Province, China: A comparison between 2006 and 2014

“…Consistent with previous serosurveillance data (Chen et al, 2014;Lee et al, 2011;Gallone et al, 2017), a continuous high level and no change in anti-HAV seroprevalence was found for the older population (>30 years of age) in the 2006 and 2014 surveys. This is explained by the fact that these older people were more likely to have been exposed to HAV due to poorer hygiene and sanitation during early childhood, at a time when the disease was endemic in China.…”

Enteric Viruses and Fecal Bacteria Indicators to Assess Groundwater Quality and Suitability for Irrigation

“…Following a large epidemic in 1998, a vaccination program for toddlers and preadolescents was introduced in this region. Consequently, the incidence of disease has dramatically decreased between 2005 and 2014, which could explain our study results [ 43 ]. However, the increase of susceptible subjects and the permanence of environmental and behavioral risk factors may determine the onset of new epidemics in the case of re-entry of the pathogen, as Ajelli et al [ 44 ] theorized through a mathematical predictive dynamic model.…”

Hepatitis A vaccination and its immunological and epidemiological long-term effects – a review of the evidence

“…139,145 Similar data were reported for regional UMVs regarding disease incidence, 86,152,154 outbreak frequency, 158 and regarding hospitalizations. 166 Other epidemiological parameters indicating nationwide or regional success or expected effects of UMV were: herd protection of untargeted age groups 22,146,147,149,154,160 (section 4.2), a rise in seroprotection rates in targeted children/adolescents 153 or young adults, 161 susceptibility (seronegativity) shift toward older age groups, 163,172 a disease burden shift toward older age, 154,156,[171][172][173][174] international travel becoming a predominant risk factor for HAV transmission, 171,172 a decline in the rate of infection-induced high anti-HAV levels in non-vaccinated toddlers, 159 a declining rate of HAV among all viral hepatitis cases 151 and finally, declining HAV positivity of river water samples. 144 To sustain HAV elimination, a certain vaccination coverage of the pediatric target population should be maintained.…”