Changes in hepatitis A virus (HAV) seroprevalence in medical students in Bangkok, Thailand, from 1981 to 2016

Abstract

ObjectiveThis study aimed to determine the seroprevalence of anti-HAV IgG in Thai medical students in 2016 compared with the previous data and to demonstrate the cross-effective strategy to screen HAV seropositivity.ResultsSera from 176 first-year medical students (age 19.07 ± 0.59 years; 50% female) at a university hospital in Thailand were tested for anti-HAV IgG. Data from HAV vaccination records and questionnaires were also collected. HAV seropositivity was unexpectedly high (62.5%, n = 110). 37.5% (n = 66) had an HAV vaccination record. Of these, 60.6% received the full HAV vaccination series, 4.5% received one HAV vaccination, 34.8% did not receive HAV vaccination, and 3.0% had natural HAV immunity. The long-term efficacy of HAV vaccination was at least 97.5% over a mean of 15.55 ± 2.44 years. There was a significant difference in immunity between students with (66.7%) and without (50.9%) vaccination records (P = 0.028). Most of the student’s parents had a bachelor’s degree or higher (87.9%; n = 272) and above average income (mean 17,000.76 ± 194.22 USD/person/year). Parental education and socioeconomic status influenced vaccination accessibility in these medical students. Screening of vaccination records instead of routine anti-HAV IgG testing is a cost-effective and reliable strategy to determine HAV immunity in medical students in Thailand.

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

“…Real-time seroprotection following immunization with two doses (or three doses with lower antigen content than currently licensed) of inactivated monovalent HAV vaccines, or of a HAV antigen containing combined hepatitis A + B vaccine, has been investigated over ≥ 10 years in children (incl. infants & toddlers), [42][43][44][45][46][47][48][49][50][51][52][53] adolescents 54,55 and adults [56][57][58][59][60] (Table 2). These studies show quite consistently that healthy adults, as well as children and adolescents, will, following standard immunization schedules (0/6-12 months), be real-time seroprotected for up to 15-20 years in 95-100% of vaccinees, while mathematical modeling estimations extend this period up to 30-40 years in 84-97% of subjects.…”

Seroprevalence and incidence of hepatitis A in Southeast Asia: A systematic review

“…These results were in high contrast with the results from other regions which were closer to the nationwide average ( Fig 2C ). Results from 5 other studies from Thailand provided estimates of HAV exposure among medical students and medical cadets [ 28 , 36 , 52 ] and at specific age groups [ 30 , 35 ].…”

“…Reports on the incidence of hepatitis A were found for four countries in Southeast Asia including Malaysia [ 47 ], Singapore [ 51 , 52 ], Thailand [ 51 ] and the Philippines [ 48 ], where hepatitis A is a notifiable waterborne disease. Please refer to S1 Fig for a geographical overview of this review.…”

A Comparison of Clinical Manifestations and Outcomes between Acute Sporadic Hepatitis A and Hepatitis E Infections in Thailand

“…This gradual attenuation in HAV seroprevalence could plausibly be attributed to improved sanitation standards over the intervening years. However, it is noteworthy that the prevalence of anti-HAV IgG in Thai medical students experienced an upswing, ascending to 63.07% in 2012, which might be attributed to the launching of the HAV vaccine in Thailand, which has been available since 1995 [ 29 ]. Typically, the HAV vaccine is administered to children from middle- to high-income families during their kindergarten years.…”