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Letters to the Editor Indian Pediatrics 2001; 38: 1322-1325 |
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Reply |
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We defend the methodology of the review. As has been highlighted adequately in the review, for estimating the magnitude of hepatitis B in our country, it is important to have samples representative of the population; if this data is not available, then one has to look at data closest to this. We hope that Drs. John and Abraham will agree that professional donors and other high risk groups are not representative samples and were, therefore, excluded from review. Also, the magnitude of problem cannot be estimated accurately if the test used is not sufficiently sensitive and specific; therefore only those studies that used a 3rd generation test for HBsAg detection were included. These reasons have been mentioned in the article. While we agree that acute complications of hepatitis B are important, we reiterate that it is the risk of chronic sequelae of HBV infection that forms the basis of immunization against hepatitis B. The Purpose of Immunization Our statement, ‘the goal of immunization program against hepatitis B is to reduce the incidence of, and possible eliminate hepatocellular carcinoma and chronic liver disease by reducing the number of hepatitis B carriers in the population’; refers to the final goal of immunization with hepatitis B vaccine. The statement in no way intends to imply that the carriers will also be vaccinated; we are talking about immunization and not therapy. There is no doubt that immunization during infancy will protect against infection and therefore, prevent chronic liver disease and hepatocellular carcinoma due to chronic HBV infection. While HBV causes acute hepatitis, the problem does not appear to be common/prevalent enough to alone justify universal immunization. Most of acute hepatitis (39- 63%) in India is due to hepatitis A and hepatitis E viruses(2-5). If prevention of acute complications is the major issue, then probably hepatitis A vaccine should get a priority. We have clearly stated the lack of sufficient data to calculate the age-specific incidence rates of the infection. We have also emphasized the need for such data to assess the magnitude of problem and to formulate appropriate immunization strategy. We have amply discussed in our article the differences in the consequences of hepatitis B infection at different age groups, which has been reemphasized by the Drs. John and Abraham. The greatest burden of chronic liver disease will be due to infection acquired by perinatal transmission and not due to infection acquired later in life. This may be reason for the high disease burden in countries like Taiwan with high carrier rates; most of the carriers are due to perinatally acquired infection. We have tried in the review to quantify the magnitude of various sequelae with available data. We feel that the detailed discussion about other aspects of childhood immunization is not relevant here. In India, the ‘desire’ for catch up immunization as ‘exemplified’ by the un-expected popularity of HBV immunization camps for all groups is largely due to the misleading propaganda. Most of these campaigns greatly overestimate the risk of death/hepatocellular carcinoma without giving the basis for such conclusions. We hope that the ‘experts’ will notice this and try to prevent various bodies from embarking on false, but frightening ad campaigns. Definitely, there is a lot of commercial interest in these types of campaigns. The True Prevalence We have highlighted sufficiently the pitfalls in the estimation of the carrier rates. We believe that in absence of extensive data from community, available data has to be analyzed considering the limitations of such an exercise. It is for this reason that the available data has to be screened carefully. The type of test used, and the population screened are important and not ‘artificial’ criteria for such analysis. Regarding the voluntary donors, we are not aware of any written policy to inform the donors of their HBsAg status to discourage HBsAg positive donors from further blood donations. In absence of such a policy, Drs. John’s and Abraham’s argument about voluntary donors being a poorer quality sample than replacement donors is not valid. In fact, replacement donor group always has a chance of contamination by the professional donors. We hope that the Drs. John and Abraham agree that professional donors are not appropriate for the purpose of estimation of prevalence. We are surprised that the Drs. John and Abraham have relied on the ‘extensive’ review by INASL(6). We hope that they had examined the INASL review as critically. First, the review by Thyagarajan et al. included some studies done on professional donors and high-risk groups. Second, in order to arrive at a mean figure, Thyagarajan et al. merely took a mean of all the prevalences reported(6). This is by no means an appropriate analysis. If the studies on the professional donors and high-risk group are excluded, and the data is pooled by adding the sample sizes and the absolute number of carriers in each sample, the mean prevalence will be 2.6% and not 4.7%. This sufficiently highlights the overestimation of the problem by inappropriate means. It is surprising that the ‘experts’ have believed and widely used this figure. In comparison our analysis is more transparent and authentic, and not ‘misleading’ or ‘flawed’ as interpreted by the Drs. John and Abraham. The Deficiencies in the Method of Analysis We picked up the figure ‘3%’ to drive home the message of overestimation of the true prevalence because the weighted mean for carrier rate in blood donors was about 2.9% and that in pregnant women 2.8%. So, there was a basis for selection of this figure. Just looking at the number of studies with carrier rates in different ranges is not the appropriate way to arrive at such a figure. The blood donors being a minority and women being less likely to become carriers is not enough to suggest an upward revision of estimate of carrier rate in the country. We will like to clarify that even if the specificity of the test is 99%, the true prevalence will still be lower than the ‘test-positive’ prevalence of about 3% unless the sensitivity of the test is less than 66%. We believe that the available tests certainly have a better sensitivity. The Utility of HBV Immunization Program We reemphasize our conclusion that the magnitude of problem of hepatitis B virus in India has been overestimated. Our review clearly shows that the risk of problems after HBV infection is also definitely over-estimated(1). In this era of evidence-based medicine, the ‘experts’ are expected to evaluate the data critically and provide concrete evidence for any recommendation that is made and not discourage the efforts towards this end. The statement ‘further data regarding the true extent of the problem is required so that the utility of the vaccination program can be evaluated objectively’ highlights the need for proper assessment of the magnitude of the problem at present, so that the impact of the vaccination could be judged on the basis of objective data and not estimates alone. We would once again like to highlight that Drs. John and Abraham have chosen to believe the figure of 4.7% as given by the INASL, inspite of the serious problems with the derivation of this figure. Recently, the need for universal hepatitis B immunization has been questioned and the overestimation of the disease burden due to HBV infection highlighted(7). The decision about the inclusion of a vaccine in UIP will be based, among other issues, on the extent of the problem and the cost effectiveness, provided safe and effective vaccines are available. In addition, the ‘experts’ opinion is bound to influence such decisions. In a limited resource setting where vaccines against multiple infections may be required, objective data should be used to prioritize inclusion of vaccines in UIP. We hope that the whole issue is addressed based on evidence and not on ‘opinion’. Rakesh Lodha, |
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