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Seroepidemiology of Hepatitis B and D

The seroepidemiologic trend of HBV infection was studied by analyzing data gathered from various sources, including those on the general public as well as people at higher risk of infection.

HBV markers in local Chinese

In a study conducted by Yeoh et al6 in 1978-1979, 16,334 subjects were tested for markers of HBV. The study population comprised 15,660 blood donors of Chinese descent between the ages of 16-40, 329 patients over the age of 41, and 345 patients between the ages of 1-15, hospitalized for non-hepatic diseases. The findings are summarized in tables 7 and 8.

age group male female total
  no. tested %+ve no. tested %+ve no. tested %+ve
1-5 82 3.7 40 2.5 122 3.3
6-10 76 5.3 41 0 117 3.4
11-15 55 9.1 51 9.8 106 9.4
16-20 4833 9.2 2770 6.2 7603 8.1
21-30 5485 12.8 1572 6.4 7057 11.4
31-40 874 10.8 126 2.4 1000 9.7
41-50 225 10.2 35 5.7 260 9.6
>50 52 7.7 17 11.8 69 8.7
total 11682 11.0 4652 6.1 16334 9.6

table 7 - prevalence of HBsAg in Chinese population in 1978-1979

The overall prevalence of HBsAg was 9.6%. A significantly higher prevalence of 11.0% was noted in males compared to the 6.1% in females (p<0.01).

age group no. tested %+ve no. tested
1-5 10.4 16.8 13.6
6-10 18.4 5.6 13.7
11-15 49.1 29.0 37.7
16-20 13.8 26.2 35.6
21-30 47.3 40.8 45.8
31-40 62.6 29.7 54.5
41-50 64.7 65.7 65.4
>50 73.7 86.8 77.5
total 49.3 33.3 42.9

table 8- prevalence of hepatitis B infection (either HBsAg or anti-HBs positive) in the Chinese population 1978-79

The overall prevalence of hepatitis B infection, defined as the rate of positive results in either HBsAg or anti-HBs in the population In Hong Kong was 42.9% in 1978-79 (table 7).

New Blood Donors

From the data provided by the Hong Kong Red Cross Blood Transfusion Service (HKRCBTS), the prevalence of HBsAg in new blood donors has decreased from 9.2% in 1988 to 5.57% in 1996 (figure 4). The total number of new blood donors varied between 35,000 to 45,000 per year.

year HBsAg+ve (%)
88 9.2
89 8.57
90 7.97
91 8.04
92 7.38
93 6.7
94 5.88
95 5.99
96 5.57

fig 4 - prevalence of HBsAg in new blood donors

Antenatal women

Blood samples have been taken from antenatal women for HBsAg testing since 1983. The prevalence of HBsAg has decreased from >11% in 1983-1987 to 9.7% in 1996 (figures 5 and 6).

year no. tested no. (%) +veHBsAg
83 11216 1260 (11.2)
84 15892 1721 (10.8)
85 22311 2589 (11.6)
86 37923 4511 (11.9)
87 37444 4248 (11.3)
88 39883 4303 (10.8)
89 34293 3880 (11.3)
90 31749 3574 (11.3)
91 30075 3278 (10.9)
92 31394 3391 (10.8)
93 34221 3456 (10.1)
94 32470 3247 (10.0)
95 30962 3016 (9.74)
96 31508 3072 (9.7)

Fig 5 - HBsAg prevalence in antenatal women

no. tested (% positive HBsAg) according to age group
year <15 15-19 20-24 25-29 30-34 >34
1989 304(9.9) 976(11.4) 4622(11.1) 12419(11.5) 7591(11.6) 2548(11.9)
1990 447(6.9) 1044(10.3) 4671(13.4) 15228(10.7) 7639(12.6) 2780(12.9
1991 86(5.8) 987(10.7) 4620(10.7) 13151(10.4) 8168(11.5) 3063(11.8)
1992 50(4.0) 928(9.6) 5065(11.4) 13093(10.6) 8788(10.6) 3470(11.7)
1993 30(10.0) 984(9.0) 5589(10.5) 12345(10.3) 9395(11.6) 3798(11.0)
1994 50(6.0) 951(7.8) 5723(9.8) 11590(9.7) 10158(10.6) 3998(10.4)
1995 474(4.3) 922(8.4) 4979(9.7) 10619(9.6) 10112(9.8) 4283(10.3)
1996 97(6.2) 842(7.8) 4765(10.3) 10137(9.5) 9759(9.5) 5908(10.6)

table 9 - prevalence of HBsAg among antenatal women by year and age

Fig 5 - HBsAg prevalence in antenatal women

When compared with clients of the Premarital Package Service (section 5.4), a relatively high rate of HBsAg carriage is evident. This phenomenon may be explained by a recent study of Kwan et al7 , which found that a significant proportion (39.7%) of the antenatal population in Hong Kong were Mainland Chinese with a different carrier rate of HBsAg. Whereas the Mainland Chinese had a carrier rate of 13.1%, local Chinese had a lower rate of 8.4% (p<0.001). The overall rate of 10% is mainly the weighted mean of the 2 population groups (table 10)

ratio (%) +ve HBsAg
age Hong Kong China all
15-19 0/33 (0) 0/9 (0) 2/47 (4.3)
20-24 12/156 (7.7) 23/132 (17.4) 38/373 (10.2)
25-29 35/436 (8.0) 52/379 (13.7) 91/910 (10.0)
30-34 44/460 (9.6) 36/331 (10.9) 85/851 (10.0)
>35 11/135 (8.1) 18/134 (13.4) 31/299 (10.4)
total 102/1220 (8.4) 129/985 (13.1) 247/2480 (10.0)

table 10 - HBsAg prevalence of Hong Kong and Mainland Chinese antenatal women by age group

Premarital screening

Data derived from clients who attended the Premarital Package Service (PMPS) of the Family Planning Association of Hong Kong showed that the prevalence of HBsAg has decreased from 10.2% in 1988 to 7.9% in 1996 (table 11).

HBsAg+ve
year total no. of cases no. %
1988 19,580 1,988 10.2
1989 17,624 1,710 9.7
1990 17,251 1,659 9.6
1991 19,142 1,831 9.6
1992 18,445 1,708 9.3
1993 19,193 1,661 8.7
1994 16,466 1,210 7.3
1995 16,798 1,320 7.9
1996 19,959 1,575 7.9

table 11 - HBsAg prevalence of clients who attended the premarital package service

University students

A hepatitis B vaccination campaign8 organized for students of the University of Hong Kong in 1992 showed that the HBsAg rate was 4.45% in 1450 male students and 2.97% in 2119 female students (age range 19-25). Anti-HBs was positive in 11.79% of male students and 11.75% of female students.

Intravenous drug user (IVDU)

Serum samples received from drug rehabilitation centres and correctional institiutions were routinely tested for HBsAg. Those negative for HBsAg were tested for anti-HBs, and those negative for both HBsAg and anti-HBs were then tested for anti-HBc. Table 12 and figure 7 summarize the results. Please note that samples taken from 1985 to 1992 were mainly from correctional institutions whereas from 1993 to 1996 mainly methadone clinics.

% +ve
year no. tested HBsAg anti-HBs anti-HBc HBV markers
1985 476 16.8 57.9 19.7 94.4
1986 540 14.6 55.2 21.3 91.1
1987 513 12.7 56.0 21.6 90.5
1988 1333 13.5 54.4 21.2 89.1
1989 668 13.3 59.0 18.9 91.2
1990 1067 13.4 59.0 15.7 90.8
1991 1517 14.4 54.4 20.5 89.3
1992 827 14.0 49.3 21.5 84.9
1993 749 14.3 43.1 12.3 69.7
1994 616 12.7 37.5 13.0 63.1
1995 190 10.5 36.8 11.6 58.9
1996 363 8.8 42.4 12.9 62.3

table 12 - prevalence of HBV markers among IVDU from 1985-1996

fig 7 - trend of HBV markers among IVDU

fig 7 - trend of HBV markers among IVDU

The ratios of both HBsAg and HBV markers have decreased. The HBV carrier rate has decreased from 16.8% in 1985 to 8.8% in 1996. The HBV markers rate decreased from 94.4% in 1985 to 62.3% in 1996.

A study by Lim et al9 showed that the prevalence of HBV markers among IVDUs had decreased from 92.7% (n=1017) in 1985-86 to 78.9% (n=1145) in 1992-93 (p<0.0001). There was a decline of HBV prevalence from 90% in 1985-86 to 73.9% in 1992-93 among those IVDU with ¡Ø5 years of drug use (p<0.0001). A decline in infection rate from 97.4 to 88.8% was noted in those who had reportedly injected for >5 years (p<0.0001) (table 13)

HBV marker
  1985-86 1992-93
age no. tested %+ve no. tested %+ve
duration of abuse <=5yr      
10-19 13 84.6 85 52.9
20-29 379 86.8 262 73.7
30-39 181 95.6 123 85.4
>40 46 95.7 39 87.2
NS 4 75 42 71.4
total 619 90 551 73.9
duration of abuse > 5yr  
10-19 1 100 0 0
20-29 78 98.7 122 86.9
30-39 216 97.2 192 92.2
>40 5 96.8 133 85.7
NS 0 0 15 86.7
totals 390 97.4 447 88.8

Table 13 - prevalence of HBV infection among intravenous drug users

Data from the same study9 showed that the prevalence of HDV has decreased from 63.1% of 149 HBsAg carriers in 1985-86 to 28.8% of 153 HBsAg carriers in 1992-93 (p<0.0001). There was a greater decline in infection rate in those with ¡Ø5 years of drug use (p<0.0001) when compared with those having used drugs for over 5 years (p<0.01) (table 14).

anti-HDV
¡@ 1985-86 1992-93
age no. tested %+ve no. tested %+ve
duration of abuse <=5yr ¡@
10-19 2 0 8 0
20-29 54 50 40 12.5
30-39 31 48.4 20 20
>40 5 80 3 66.7
NS 0 0 4 0
total 92 50 75 14.7
duration of abuse > 5yr ¡@ ¡@ ¡@
10-19 0 0 0 0
20-29 11 54.5 14 64.3
30-39 13 97.8 22 59.1
>40 11 100 14 35.7
NS 0 0 2 50
totals 55 83.6 52 53.8

table 14 - HDV prevalence among IVDU

Police officers

An ongoing vaccination campaign undertaken by the Department of Health and the Royal Hong Kong Police effectively allows screening of police officers for Hepatitis B markers. What data that are available now indicate a relatively low level of carriage. Out of the 3134 police officers that were screened, 6.2% were positive for HBsAg. On subgroup analysis, the prevalence of Hepatitis B carriers among female officers is especially low at only 3.5%. Breakdown of the data is as follows:

  male female
age no. tested no.(%) +ve for Hep B markers no.(%) HBsAg+ve no. tested no.(%) +ve for Hep B markers no.(%) HBsAg+ve
<20 1 0(0) 0(0) 0 0(0) 0(0)
20-30 616 178(29.1) 28(4.5) 249 72(28.9) 8(3.2)
31-40 1300 980(75.4) 89(6.8) 137 49((35.8) 4(2.9)
41-50 669 398(59.5) 51(7.6) 93 37(39.8) 5(5.4)
51-60 67 39(58.2) 9(13.4) 2 1(50) 0(0)
total 2653 1595(60.1) 177(6.7) 481 159(33.1) 17(3.5)

table 15 - prevalence of HBV among police officers by sex and age

Children and young adults

Blood samples from children submitted to the Virus Unit for virology examination were tested for HBsAg and anti-HBs in 1990 and 1993. It was found that the prevalence of HBsAg had decreased in all age groups (Table 16).
For the testing in 1993, the prevalence of anti-HBs has decreased from 91.5% in children of age 1 to <2 years to 69.2% in children of age 4 to <5. This might be due to the fall of anti-HBs level after vaccination. Missed vaccination may also have contributed to the difference. Hepatitis B vaccination has been offered to all newborn since late 1988.

  no. tested %+ve for HBsAg %+ve for anti-HBs
age (yr) 1990 1993 1990 1993 1990 1993
1-<2 100 47 0 0 71 91.5
2-<3 98 38 2.0 0 39 89.5
3-<4 96 36 6.3 2.8 10.1 80.6
4-<5 98 26 0 0 16.7 69.2
5-9 97 123 7.2 2.4 12.9 50.4

table 16 - prevalence of HBV markers among children

A study being conducted by Albert Lee5 of the Chinese University also examined the prevalence of HBV in adolescents (aged 11-20). Preliminary data indicate the prevalence of HBsAg is 5.8% and that of HBV markers 17.0%. These results are in line with those released recently by the Cancer Crusade Angels Service Society of Hong Kong who in the last two years also conducted screening of students of secondary schools and vocational training institutes. In their studies, the overall carrier rate of HBsAg was found to be 6.5% and 5.8% in 95 and 96 respectively. Breakdown according to age and sex is as follows (tables 17 and 18).

  male female
Age no. anti-HBs+ve(%) HBsAg +ve (%) no. anti-HBs+ve(%) HBsAg +ve (%)
11-15 214 40 (18.7%) 22 (10.3%) 69 19 (27.5%) 3 (4.3%)
16-20 610 120 (19.7%) 54 (8.9%) 495 91 (18.4%) 31 (6.3%)
21-25 219 27 (12.3%) 5 (2.3%) 224 40 (17.9%) 4 (1.8%)
total 1043 187 (17.9%) 81 (7.8%) 788 150 (19.0%) 38 (4.8%)

table 17 - prevalence of HBsAg in young adults in 1995

  male female
Age no. anti-HBs+ve(%) HBsAg +ve (%) no. anti-HBs+ve(%) HBsAg +ve (%)
11-15 873 134 (15.3% 22 (10.3%) 878 125 (14.2%) 52 (5.9%)
16-20 527 94 (17.8%) 31 (5.9%) 562 108 (19.2%) 27 (4.8%)
21-25 99 27 (12.3%) 6 (6.1%) 94 25 (26.6%)) 5 (5.3%)
total 1499 244 (16.3%) 91 (6.1%) 1534 258 (16.8%) 84 (5.5%)

table 18 - prevalence of HBsAg in young adults in 1996

Female commercial sex workers

626 consecutive female commercial sex workers were screened for markers of hepatitis B when they attended the Yaumatei Social Hygiene Clinic from 1 Mar 95 to 3 Mar 97. 40 (6.4%) were HBsAg+ve, 346 (55.3%) were anti-HBs+ve, and 240 negative for both markers.

Health care workers

In 1983, a total of 3,347 health care workers were screened for HBV markers in a study by Yeoh et al10. The results are as shown in table 19.

  HBsAg anti-HBs markers of HBV
pre-entry (n=187) 7.5% 20.3% 30.8%
0-5 yr (n=1781) 8.9% 27.4% 40.8%
5-10 yr (n=666) 9.3% 38.4% 52.5%
>10 yr (n=713) 10.8% 43.1% 58.7%

table 19 - HBV markers among health care workers in 1983

From 1983 to 1991, another 26,188 health care workers were screened for HBV markers prior to vaccination - 6.2% were found to be positive for HBsAg, while 26.4% were positive for anti-HBs.
In an HBV vaccination campaign organized for the staff of the Department of Health in 1995, 719 health care workers were screened for HBV markers - 7.0% were positive for HBsAg and 36.3% positive for anti-HBs.
Among these 719 staff who had undergone blood screening, 689 could be traced for their particulars. 220 were male and 469 female. The age breakdown is as shown in table 20.

age
markers
no. of staff (%)
<21 21-30 31-40 41-50 51-60 total
HBsAg+ve 0(0) 5(5.7 17(6.7) 15(6.6) 10(8.8) 47(6.8)
anti-HBs+ve 3(42.9) 28(32.2) 88(34.9) 92(40.2) 40(35.1) 251(36.4)
HBsAg/anti-HBs
(-/-)
4(57.1) 54(62.1) 147(58.3) 122(53.3) 64(56.1) 391(56.7)
total 7(100) 87(100) 252(100 229(100) 114(100) 689(100)

table 20 - Hepatitis B markers in health care workers screened in 1995

In another study by the Department of Health in 1989, results of HBsAg screening in 1,087 ambulance officers are shown in table 21.

age no. tested %+ ve
15-24 124 3.2
25-34 679 11.5
35-44 251 12.0
>45 33 12.1

table 21 - HBsAg prevalence among ambulance officers in 1989

Lim et al11 report that among 5825 health care workers who were screened in 1992 and 1993, 255 (4.7%) were positive for HBsAg, 2223 (38.2%) were positive for anti-HBs, and 3347 (57.5%) lacked both HBV markers. A recent vaccination campaign (1995-96) for the staff of the Caritas Medical Centre (CMC) identified 39 carriers of HBsAg among 921 health care workers, an overall prevalence rate of 4.2%

  no. of staff (%)
markers male female
HBsAg+ve 15(11.2) 243(3.0)
anti-HBs+ve 60(44.8) 415(52.7)
HBsAg/antiHBs (-/-) 59(44.0) 348(44.2)
total 134(100) 787(100)

prevalence of HBV in staff of CMC

People with HIV/AIDS

Data from the AIDS Unit of the Department of Health indicate a relatively high level of HBsAg carriage among those who have results of HBV markers available. As of Dec 96, the overall rate of HBsAg positivity approached 16%.

sex no. +ve HBsAg (%) no. +ve anti-HBs (%) total
male 21 (16) 60 (45.8) 131
female 2 (15.3) 6 (46.1) 13
total 23 (15.9) 66 (45.8) 144

table 22 - prevalence of HBsAg in people with HIV/AIDS

Prevalence of HDV among HBV carriers

From 1985 to 1987, 198 patients with HBV related liver diseases were screened for anti-HDV antibody in a study by Leung et al12, only 1 patient was detected positive.

Summary of HBsAg rate among different groups

Figure 8 summarizes the above data on HBV carrier rate among different groups. The HBsAg rates among all the different groups have been falling over time.

fig 8 - trend of HBsAg rate in different groups