The current claims of Hepatitis B virus (HBV) carrier rate in India are highly exaggerated, unscientific and misleading. A series of errors is being made in estimating the burden of HBV disease and its significance. These errrors must be corrected, and we must scientifically assess the burden of morbidity, mortality and consequent loss of life- years due to HBV in India. Finally, we must also discuss the various options for a HBV vaccination strategy in India on the basis of cost effectiveness and logistical feasibility. We are unaware of any such exercise by the Indian Association of Paediatrics before its strong recommendation of universal immunisation of Indian children against HBV.

Frightening figures
Most doctors seem convinced about the overwhelming danger of HBV infection in India based on frightening figures put forth by experts who claim that the carrier rate in India is 4.7 per cent with an estimated carrier population of 42.5 million (1). These widely- quoted estimates, based on the results of 19 studies, suffer from three types of errors.

First, the studies are all one- time cross- sectional studies of prevalence of HBsAg positivity. Positivity is different from a carrier state — the persistence of infection for six months or more (2).

Second, many of these studies are based on data from blood bank donors, including professional blood donors who are known to have a higher prevalence of HBV infection. One study reports on dental professionals, another high risk group. These groups cannot be used to estimate prevalence in the general population.

Finally, the average prevalence of 4.7 percent has been arrived at not as a weighted average but by calculating the simple average of the numbers in the individual studies.

A more accurate estimate of the carrier rate — a carrier being someone who has tested positive for HBsAg in two tests six or more months apart — using the same data in the 19 studies, and after excluding the professional blood donors and dental personnel and those studies in which the numbers tested are not mentioned (and taking into account the positive predictive value of the test being used currently) works out to be 1.42%, with a carrier pool of 12.75 million (3).

It is also important to note that, contrary to the current assertions (4), not all HBsAg positives are highly infectious. The prevalence of highly infectious carriers (“ Hbe positives”) is much lower than the estimate of 24.43 per cent of HBsAg positives or approximately 10 million (1). We arrive at the much lower figure of 3.26 million highly infectious carriers (3).

Is it a public health problem?
Some people have argued that HBV is a major public health problem. “Liver disease due to HBV infection is considered to be the fourth or fifth most important cause of mortality in the most productive period of life, 15- 45 years (4). Approximately 25 per cent of carriers are expected to die of chronic sequelae of the infection — cirrhosis and primary hepatocellular carcinoma (5). In fact, the danger of chronic infection and chronic sequelae from HBV infection is much less than that. Recent observations suggest that the true rate of chronic infection is as low as one per cent in normal, immunocompetent young adults (6), not five per cent to 10 per cent. Even among these carriers, about two per cent clear the virus every year.

We do not have adequate data on prevalence of HBsAg positivity in India, on the carrier rate in different age groups and on the prevalence of acute and chronic HBV diseases and their sequelae in these age groups, to estimate the number of life years lost due to HBV compared to other (especially vaccine preventable) diseases in India. While we do not attempt this here, a range of studies suggests that the overall burden of disease is much lower than it is made out to be (3). Before recommending Universal Immunisation of HepatitisB vaccine, it is necessary to estimate on the basis of available data (Western or Indian), the life years lost per lakh of population due to Hepatitis B. This will form the basis for estimating the cost- efficacy of this vaccine.

Immunisation strategies
Supporters of universal immunisation quote the US decision to switch from selective, high- risk vaccination to universal immunisation. However, there is a vast difference between the predominant mode of transmission and age distribution of acquisition of HBV infection in developing and in developed countries. Most HBV infections in the developed world occur among adults, primarily through sexual transmission (2), whereas perinatal infection is the most important mode of HBV perpetuation in developing countries (6).

For these reasons, we should consider the option of selective immunisation of newborns of HBsAg positive mothers or of all pregnant women. Logistically this is feasible, because unlike the high risk groups in the US, this vulnerable group in India (newborns/ infants) is visited by the health services anyway, for immunisation work.

In the context of other health programmes
Lastly, in allocating resources to the vaccination programme, its expense, efficacy and contribution to the prevention of diseases in India must be placed in the context of other health programmes in India. For example, the cost of vaccines of all six vaccine- preventable diseases in the Expanded Programme of Immunisation was Rs 17 per child in

1992 (7), which may have increased to Rs 30. Even at a subsidised Rs 100 per child, the vaccine costs alone of vaccinating just newborns against HBV would be Rs 2,500 million per year. Extending the programme to the 0- 4 or 5- 14 age groups could send costs to Rs 12,730 million annually. To put these figures in context, this year´s budget for malaria is Rs 2,240 million and TB is Rs 1,050 million (8).

We also need an estimate of the programme´s cost efficacy. The cost efficacy of different immunisation strategies depends on the cost per life year saved from immunisation, and cost per unit reduction in the infectious pool. Can we afford to introduce a vaccination strategy with a cost efficacy of say Rs 15,000 per life year saved when our per capita annual income is around Rs 10,000?

Need for debate
This call for better studies on prevalence and burden of disease, for estimates of cost efficacy and for a strategy towards new vaccines is becoming particularly important as newer vaccines come into the Indian market each year, and pressures are exerted to include these vaccines in the national health programmes.

References:
1. S. P. Thyagarajan, S. Jayaram, B. Mohanvalli. Prevalence of HBV in the general population of India, in Hepatitis B in India (Ed.) S.K.Sarin, A.K.Singhal, CBS Publishers and distributors, 1996, p.9.
2. Public Health and Preventive Medicine, Maxcy-Rosenau-Last, 13th edition, 1992, p. 134.
3. Phadke A and Kale A: Some critical issues in the epidemiology of HBV in India (under publication)
4. B.N.Tandon. Dimensions and issues of HBV control in India, in Sarin-Singhal (Ed.) op.cit, p.1.
5.Kant Lalit, Hall Andrew. Epidemiology of childhood Hepatitis-B in India: vaccination related issues. Indian Journal of Paediatrics 1995, 62: 0635.
6. Harrisons Principles of Medicine. 1998 p. 1689
7. Phadke Anant, Fernandes Audrey, Sharda L., Mane Pratibha and Jesani Amar: A study of supply and use of pharmaceuticals in Satara District. Foundation for Research in Community Health, 1995, Page 11.
8. Economic Intelligence Service, CMIE,Public Finance, May 1998, p. 8.

Additional reading:
1. Textbook of Preventive and Social Medicine, K. Park, 15th edition 1997.
2. Alward WLM, Mcmohan B. J., Hall D. B. et. al.: The long term serological course of asymptomatic Hepatitis B Virus carriers and the development of primary hepatacellular carcinoma. Journal of Infectious Diseases. 1985: 15: 605, table 1.
3. Gupta I., Sehgal R. et al.: Vertical transmission of Hepatitis B in North India.Journal of Hygiene, Epidemiology, Microbiology and Immunology, 36, 1992, No. 3, P. 265, table 1.
4. Elavia A. J. and Bankar D. D. : Prevalence of Hepatitis B surface antigen and its subtypes in high risk group subjects and voluntary blood donors in Bombay. Indian Journal of Medical Research 1991 September [A] 93 280- 285.
5. Agarwal R., Naik S. R.: Cost efficacy evaluation of inclusion of Hepatitis- B vaccine in e xpanded programme of immunization, in Sarin S. K., Singhal A. K. op. cit, P. 206 to 216.
6. Lodha Rakesh, Jain Yogesh: Need for universal Hepatitis B immunisation in India: A review of literature. (under publication)