In a study conducted by Chin et al1 of the Department of Medicine, University of Hong Kong, stored sera from 702 healthy subjects collected between 1987-1989 were tested for antibody to hepatitis A. Over 90% of the healthy subjects aged above 40 were positive for anti-HAV. Data collected in 19781 and 19932 were available for comparison. Whereas the prevalence of anti-HAV in people older than 30 years old were similar, there has been an obvious decrease over the years In the prevalence in the younger people. Figure 3 presents the change in age-specific prevalence of anti-HAV over time. The bars representing young age groups have become lower, indicating that people are contracting HAV at an older age. Relatively more young adults are therefore becoming susceptible to HAV.
|age group||% +ve anti-HAV|
In another study3 conducted by the Virus Unit of the Department of Health in 1989, 1028 serum samples collected from individuals who attended a health exhibition were tested for anti-HAV. The age-specific prevalence of anti-HAV is shown in table 3. The results are comparable with those of the study by Chin et al.
|age||no. tested||% positive|
table 3 - age specific prevalence of anti-HAV
In an HAV vaccination study conducted by Lo et al4, Department of Health, in 1993, 310 health care workers were screened for anti-HAV. The results are shown in table 4. The seroprevalence is similar to that of the general public.
|Sex/Age||No tested||% anti-HAV positive|
table 4 - prevalence of anti-HAV among health care workers
|heaptitis A IgG||11-12||13-14||15-17||18-20||total|
|positive||3 (1.7%)||21 (4.9%)||41 (6.3%)||46 (14.2%)||111 (7.0%)|
|negative||172 (98.3%)||409 (95.1%)||611 (93.7%)||277 (85.8%)||1469 (93.0%)|
|total||175 (100%)||430 (100%)||652 (100%)||323 (100%)||1580 (100%)|
table 5 - correlation between age and anti-HAV status
In two successive hepatitis awareness campaigns held by the Hong Kong Academy for Performing Arts, new students were screened for anti-HAV. The prevalence was 11.9% in 94 and 10.7% in 96.
|no. tested||% anti-HAV positive||no. tested||% anti-HAV positive|
table 6- prevalence of anti-HAV in college students