Estimating the burden of hepatitis B virus infection in Laos between 2020 and 2021: A cross-sectional seroprevalence survey

Abstract

Background: Laos is considered highly endemic for persistent infection with hepatitis B virus (HBV). To eliminate this burden, it has gradually implemented universal anti-hepatitis B immunisation of newborns over the past two decades.

Methods: Using VIKIA® HBsAg, a rapid test for the qualitative detection of the HBV surface antigen, we conducted between Sep 1st, 2020 and Aug 31st, 2021 the largest prospective prevalence survey ever in Laos. This survey included blood donors (BD, n = 42,277), patients attending care in capital and provincial hospitals (n = 37,347) including attending mothers (n = 20,548), HIV-infected patients (n = 7439, recruited from 2009 to 2020), students from the Health Sciences University (n = 609), and outpatients (n = 350) coming for diagnosis at the Center Infectiology Lao-Christophe Mérieux in Vientiane. In total, 88,022 persons were tested, representing approximately 1.22% of the national population. To reach a reasonable estimate of HBsAg prevalence in Laos, we segmented the population according to three variables, age (≤20 years as a cut-off), sex, and geographical origin. BD values were used to estimate HBsAg prevalence in patients aged <20 while hospital survey prevalence was used to estimate the prevalence in those aged older than 20 years.

Findings: We observed an HBsAg seroprevalence ranging from 2.6% in blood donors to 8.0% in HIV-infected patients. In BD, men were significantly more at risk to be carriers than women (RR = 1.2, P = 0.00063). For BD, attending mothers, or HIV-infected patients, HBsAg was significantly more prevalent in northern Laos (5.1-8.4%) than in central (2.0-8.1%) or southern parts of the country (2.2-6.9%), thereby delineating a North-to-South gradient.

Interpretation: We considered that HBsAg prevalence probably ranges between 5.0% and 6.0% of the total population. Thus, we consider that Laos may no longer be highly endemic for chronic HBV infection but rather a country with intermediate endemicity.

Funding: The funding sources were the Agence Universitaire de la Francophonie, the French Government, the French Institute for Sustainable Development (IRD), and European Union's Horizon 2020 Marie Sklodowska-Curie Actions (MSCA) - Research and Innovation Staff Exchange - (RISE) under grant agreement N° 823935.

Keywords: Endemic country; Hepatitis B virus; Laos; Southeast Asia; Universal Immunization.

Figure 1

Prevalence of Hepatitis B virus surface Antigen (HBsAg) in the different subsets of participants and in the Hospital-based survey. A. Bar chart representing HBsAg prevalence by % in the 42,277 blood donors, the 37,347 patients attending care in the different participating hospitals, and the 7439 HIV-infected patients, according to the different age classes. B. Heterogeneity of HBsAg prevalence in the different components of the hospital-based series. It should be noticed that all patients except those infected with Human Immunodeficiency Virus, HIV(+), were recruited between September 2020 and August 2021. The Human Immunodeficiency virus-positive series [HIV(+)] was enrolled between 2009 and 2020.

Figure 2

Differential Hepatitis B virus surface Antigen (HBsAg) prevalence according to sex or geographic origin. A. HBsAg seroprevalence according to sex in the five population subsets investigated. B. HBsAg seroprevalence according to the place of sampling in blood donors, mothers attending care in maternity departments, and Human Immunodeficiency Virus-infected patients [HIV(+)].

Figure 3

Map of Laos representing the prevalence of Hepatitis B virus surface Antigen (HBsAg) in the different provinces A. In blood donors, B. In patients attending care in hospitals. C. In Human Immunodeficiency Virus-infected patients [HIV(+)].

Figure 4

Bar-Charts differentiating Hepatitis B virus surface Antigen (HBsAg) prevalence according to age and sex. A. Bar chart representing HBsAg prevalence in blood donors according to sex, age, and region of origin. B. Bar chart representing HBsAg prevalence according to sex and age in the hospital-based cohort. C. Bar chart representing HBsAg prevalence according to sex and age in Human Immunodeficiency Virus-infected patients [HIV(+)].

Figure 5

Estimated distribution and seroprevalence of Hepatitis B virus surface Antigen (HBsAg) in the three large regions of Laos.