Hepatitis A virus vaccination strategy and pre-immunization screening of Bangladeshi children

Introduction Hepatitis A virus (HAV) infection occurs throughout the world but most common in developing countries.1 In these countries with high endemicity, 90% of the population is infected by 10 years of age.2 Here children are continuously exposed to the virus, which confers lifelong immunity.3 In many developing countries like India, Pakistan, Nepal several sero-prevalence studies have shown high rates of sero-positivity among child by sub-clinical infection4-9. Therefore, mass vaccination against HAV has not been recommended in endemic countries.10 Furthermore, Hepatitis-A vaccine is expensive. In Bangladeshi children, limited data are available regarding the sero-prevalence of HAV antibody.11 In this context, the present study was designed to see the prevalence of HAV antibody (IgG & IgM) among children of different age group and to perform a cost benefit analysis study before formulating a vaccination strategy for the children of Bangladesh. Materials & Methods A cross sectional observational study was conducted from July 2008 to June 2009. Blood was collected at blood collection centers of Bangabandhu Sheikh Mujib Medical University (BSMMU) Hospital & Dhaka Shishu (Children) Hospital (DSH). A total of


Introduction
Hepatitis A virus (HAV) infection occurs throughout the world but most common in developing countries.1 In these countries with high endemicity, 90% of the population is infected by 10 years of age. 2 Here children are continuously exposed to the virus, which confers lifelong immunity.3 In many developing countries like India, Pakistan, Nepal several sero-prevalence studies have shown high rates of sero-positivity among child by sub-clinical infection 4-9 .Therefore, mass vaccination against HAV has not been recommended in endemic countries.10 Furthermore, Hepatitis-A vaccine is expensive.In Bangladeshi children, limited data are available regarding the sero-prevalence of HAV antibody . 11 In this context, the present study was designed to see the prevalence of HAV antibody (IgG & IgM) among children of different age group and to perform a cost benefit analysis study before formulating a vaccination strategy for the children of Bangladesh.girls 115 so male:female ratio was 1.2: 1. Age distribution of the children positive for HAV antibody shows that with the advancement of age, anti-HAV positivity increases.Anti-HAV of 1-5 year age group was found to be 44.7%, it gradually increased to 70.9% in 5-10 year age group and finally to 92.6% in 10-15 year age group.Anti-HAV positivity of 5-10 year age group was significantly higher than that of 1-5 year age group (p=0.001) and antibody positivity of 10-15 year age group was significantly higher than that of 5-10 year age group (p=0.026).(Table 1.1).

Limitations of study
Small sample size, selection biasness and absence of socio-economic status are the three limitations of this study.
Fig: I Anti-HAV positivity among all children

Table 1 .1 Anti-HAV positivity with age
#Data were analysed using Chi-square (X 2 ) TestFigures in the parentheses denote corresponding percentage

Table 1 .
S, Karim ASMB, Alam J, Islam MMZ, Sarker NK, Munshi AS, Sarker S study bySheikh et al. 20reported anti-HAV positivity of 100% in 15-20 year age group.These findings are similar to the findings of our neighbouring coun-Mahmud

Table 1 .3: The cost benefit analysis of hepatitis A virus vaccination strategies
Mall et al. 2 from India (Calcutta) reported 40% anti-HAV positivity in 1-5 year age group and through gradual increase in age the prevalence reached to 97% in the >16 year age group.A recent study by Kamath et al. 5 reported anti-HAV positivity of 61.6% in 5-10 year age group and 97% in 11-15 year age group in Chennai, India.increase in age.On cost benefit analysis, the cost of vaccination with screening was almost 2 times cheaper than the cost of vaccination without screening.Therefore mass vaccination or vaccination without prior knowledge regarding the serostatus could be an unnecessary immunological assult & may not be a suitable strategy for Bangladesh in lieu of the present socioeconomic condition.Assult Recommendations Based on the present study, it may be recommended that in children less than 3 years of age vaccination without prior screening can be done.However in children of ?3 years of age, pre-vaccination screening should be done prior to vaccination as this is cost effective, safe and more rational.Further community based studies with larger sample size are required before giving a final recommendation for routine HAV vaccine to children of Bangladesh.
*113 were found negative for anti-HAV tries.