Changing Seroprevalence of Hepatitis B Virus Markers of Adults in Singapore

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FULL TEXT AT: http://www.annals.edu.sg/pdf/39VolNo8Aug2010/V39N8p591.pdf

Ann Acad Med 2010;39:591-8

Changing Seroprevalence of Hepatitis B Virus Markers of Adults in Singapore

Wei Wei Hong,1MBBS, MPH, Li Wei Ang,1MSc(Statistics), L Cutter,1MMed

(PH), MSc (Epidemiology), FAMS, Lyn ,1MBBS, MMed

(PH), FAMS, Suok Kai Chew,2MSc(PH), MSc(Epidemiology), FAMS, Kee Tai Goh,3MSc

(PH), MD, FAMS

Abstract

Introduction: We presented the fi ndings from 2 seroprevalence studies conducted

6 years

apart, so as to determine changes in the hepatitis B surface antigen (HBsAg)

positivity rate

and immunity to hepatitis B virus (HBV) among Singapore residents aged 18 to 69

years, and

to assess the impact of a 4-year catch-up hepatitis B immunisation programme for

adolescents

and young adults launched in 2001.

Materials and Methods: Two hepatitis B seroprevalence

studies (HBSS) were conducted in 1999 and 2005 based on stored blood samples

collected from

4698 participants aged 18 to 69 years during the national health survey (NHS)

1998 and from

3460 participants during the NHS 2004, respectively. Serology for HBsAg,

hepatitis B e antigen

(HBeAg) and antibody to HBsAg (anti-HBs) were tested by enzyme immunoassay in

HBSS 1999

and electrochemiluminescence in HBSS 2005.

Results: The overall age-standardised prevalence

of HBsAg among Singapore residents aged 18 to 69 years decreased signifi cantly

from 4.0%

in HBSS 1999 to 2.8% in HBSS 2005 (P = 0.002). The age-standardised prevalence

of HBsAg

in males (4.9% in 1999) and Chinese (4.7% in 1999) both decreased signifi cantly

to 2.7% and

2.8%, respectively in 2005. The overall age-standardised population immunity to

HBV (anti-

HBs >10mIU/ml) increased from 39.7% in 1999 to 42.1% in 2005 (P = 0.019). In

particular, the

age-specifi c prevalence of anti-HBs showed a signifi cant increase among those

in the age group

of 18 to 29 years from 27.9% in 1999 to 41.7% in 2005 (P <0.001) and among those

in the age

group of 30 to 39 years from 39.9% in 1999 to 44.7% in 2005 (P = 0.021).

Conclusion: There was an overall decline in the HBsAg positivity rate as well as

an overall increase in population

immunity to HBV. Following the 4-year catch-up immunisation programme, there was

a signifi -

cant increase in the immunity to HBV infection in the younger population aged 18

to 29 years