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

Abstract

Background A previous review on hepatitis A virus (HAV) seroprevalence in 2005 categorized Southeast Asia as a low HAV endemicity region. In 2010, the World Health Organization modified this from low to low/medium endemicity, pointing out that these estimates were based on limited evidence. Since then, there has been no attempt to review HAV epidemiology from this region. We conducted a systematic review of literature to collect information on HAV incidence and seroprevalence in select countries in the Southeast Asian region, specifically, The Association of Southeast Asian Nations over the last 20 years. Methodology This systematic review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. From the relevant articles, we extracted data and conducted a risk of bias assessment of individual studies. Results The search yielded 22 and 13 publications on HAV seroprevalence and incidence, respectively. Overall, our findings point to a very low HAV endemicity profile in Thailand and Singapore and evidence of a shift towards low HAV endemicity in Indonesia, Lao People’s Democratic Republic, Malaysia, the Philippines, and Vietnam. Only Singapore, Thailand, Malaysia, and the Philippines have existing HAV disease surveillance and reported incidence rates below 1 per 100,000. Several outbreaks with varying magnitude documented in the region provide insights into the evolving epidemiology of HAV in the region. Risk of bias assessment of studies revealed that the individual studies were of low to medium risk. Conclusions/Significance The available HAV endemicity profiles in Southeast Asian countries, aside from Thailand, are limited and outdated, but suggest an endemicity shift in the region that is not fully documented yet. These findings highlight the need to update information on HAV epidemiology through strengthening of disease surveillance mechanisms to confirm the shift in HAV endemicity in the region.

Seroprevalence of hepatitis A virus antibodies among children and adolescents living in Northern Thailand: an implication for hepatitis A immunization

“…In contrast, among unvaccinated adolescents, we observed the increased seroprevalence and antibody levels for HAV when compared with the other age groups, as well as the indifference in the antibody levels when compared with vaccinated individuals in the same age group. We hypothesized that some of the unvaccinated adolescents in this study might have already been exposed to HAV and/or have acquired an asymptomatic natural HAV infection during their adolescence 24 , 25 .…”

“…The absence of immunity to HAV is a significant concern for the suffering of symptomatic infection, fulminant hepatitis, and fatality among adults infected with HAV 36 . Also, since Chiang Mai province is bordered by Myanmar, where hepatitis A is still endemic 25 , there is a potential for disease outbreaks introduced by migrants crossing the border. HAV vaccine, either inactivated or live-attenuated, is well-tolerated, strongly immunogenic, and highly effective to prevent HAV infection.…”

“…Introducing HAV vaccine into the national immunization programme is one of the effective ways to protect Thai youth against infection as well as prevent future outbreaks in the high-risk areas. However, given the very low HAV endemicity profile in Thailand 11 , 25 , the recommendation of HAV vaccine among people at increased risk of infection or its consequences, including people with chronic liver diseases, men who have sex with men, people who use injection or non-injection drugs, patients with clotting-factor disorders, people at risk of occupational exposure, and international travelers to high or intermediate endemicity countries, might alternatively be a cost-effective strategy for the country 36 .…”

Defining Risk: Hepatitis A Virus in Philippine Shellfish (Oyster and Mussels)

“…In this regard, HAV endemicity remains moderate to high in Southeast Asian countries (such as the Philippines, Taiwan, and Indonesia) 3,4 . It was reported that in the Philippines 62,63 in 2015 there was a steady increase in annual cases from 440 to 563, from 2016 and 2017 showed 443 and 462 cases per year, respectively. Nearly 50% of the affected people were between 16-30 years of age.…”

“…It was reported in in 2021 6 that there was no published information on outbreaks in the Philippines, very limited information on seroprevalence for the last two decades, and that reporting up to date incidence data needs to be complemented with periodic seroprevalence surveys to fully capture the burden of HAV disease 62 .…”