WORLD HEALTH ORGANIZATION
ORGANISATION MONDIALE DE LA SANTE
REGIONAL OFFICE FOR THE WESTERN PACIFIC BUREAU REGIONAL DU PACIFIQUE OCCIDENTAL
REGIONAL COMMITTEE Fiftieth session Macao 13–17 September 1999 Provisional agenda item 13
WPR/RC50/9 30 July 1999 ORIGINAL: ENGLISH
HEPATITIS AND RELATED DISEASES
Viral hepatitis remains a significant public health problem in many countries and areas of the Western Pacific Region. In particular, hepatitis B and hepatitis C cause
considerable morbidity and mortality. In December 1998 a meeting of the Western Pacific Region Working Group on Viral Hepatitis reviewed the current situation of viral hepatitis and identified priorities for action. The meeting noted that significant progress has been made in controlling hepatitis B through immunization and in reducing post-transfusion hepatitis. However, major efforts are still needed to ensure the sustainability of immunization activities, to improve blood safety and to reduce the risk of viral transmission through medical and other practices (including unsafe injections). The epidemiology of viral hepatitis needs to be
monitored to improve planning for long-term control.
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1. INTRODUCTION
Chronic liver disease and hepatocellular carcinoma caused by hepatitis B and C are among the most important public health problems in the Western Pacific Region. Hepatitis B carrier rates in some countries and areas of the Region, especially Pacific island countries, are among the highest in the world. Twenty-five countries and areas have reported a carrier rate greater than 8% of the general population (Table 1). Of the estimated 350 million chronic carriers of hepatitis B virus (HBV) worldwide, approximately 150 million live in the Western Pacific Region. Up to 10% of these chronic carriers can be expected to die of the effects of the infection. The vast majority of infections occur in infancy and early childhood and are transmitted from carrier mothers to their infants or from child to child. Immunization of infants is the main strategy to prevent these infections, and reduce the
prevalence of chronic infection. In addition, up to 50 million people in the Region may be infected with hepatitis C (Table 2). Principal modes of infection are through transfusion of unscreened blood and blood products, and exposure to blood during intravenous drug use, unsafe injections or unsafe medical procedures. Perinatal and sexual transmission may also play a role. Hepatitis A is endemic in most countries, and is largely transmitted asymptomatically in early childhood. Although it does not at present constitute a major problem in most countries, the
epidemiology of hepatitis A is changing. With improved standards of living, infection rates in young children are declining in some countries, but it is expected that infection rates of hepatitis A will increase in older children and adults who have not developed natural immunity when they were young. From available information it appears that hepatitis E infection is more widespread than previously recognized, and in some countries hepatitis E virus is already emerging as a major cause of acute viral hepatitis. However, the epidemiology of hepatitis E is still not well understood and little information is available from most countries in the Region. Modes of transmission and availability of vaccines for different types of hepatitis are contained in Table 3.
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Table 1. Hepatitis B chronic carrier prevalence and immunization coverage rates by country/area (1992–1997) Country/area American Samoa Australia Brunei Darussalam Cambodia China a
Prevalence HBsAg (%) 7.0 0.5 8.0 12.0 12.0 10.0 11.0 10.0 4.0 12.0 2.0 31.0 12.0 12.0 5.0 12.0 12.0 14.0 n.a. 8.0 1.0 n.a. 5.0 12.0 20.0 10.0 12.0 8.0 12.0 20.0 n.a. 20.0 n.a. 19.0 12.0 8.0 90 75 82 82 82 96 18 78 90 53 100 67 100 82 75 11 94 5 100 24 6 n.a. 78 8 n.a. 79 85 17 82 69 81 82 66 98 76 88 96 n.a. 100 n.a. 1992 47 1993 49
Immunization coverage (%) 1994 68 1995 47 1996 59 1997
98 n.a. n.a. n.a. n.a.
Cook Islands Fiji French Polynesia Guam Hong Kong, China Japan Kiribati Lao People’ s Democratic Republic Macao Malaysia Marshall Islands Micronesia, Federated States of Mongolia Nauru New Caledonia New Zealand Niue Northern Mariana Islands Palau Papua New Guinea Philippines Republic of Korea Samoa Singapore Solomon Islands Tokelau Tonga Tuvalu Vanuatu Viet Nam Wallis and Futuna
79 60
86 82
65
97 98
79 92 82 91 98 87 99
79 95 87
36 n.a. 82
36 n.a. 85
66 n.a.
97 n.a. 88 88
46 82 67
47 82 89 57 93
68
70 78
92
88 86 27 100
81 100 67 73
88 90 94 100 17 100 43 100
100 98 90 43 31
100 97 89 67 96 91 68 50 90 17 91 49 66 97 65 94 49 69 95 88 72 98 99 94 73
71
82
Source: All data from the Regional Office Computerized EPI Information System as at May 1999. Missing data indicates no report that year. a Coverage data from China not reported, but estimated to be over 30% nationwide. n.a. – Not available.
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Table 2. Prevalence of hepatitis C virus infection, selected countries and areas, Western Pacific Region HCV serological surveillance Country/area Prevalence (%) Australia Cambodia China Hong Kong, China Japan Kiribati Malaysia Micronesia, Federated States of Mongolia New Zealand Papua New Guinea Philippines Republic of Korea Singapore Solomon Islands Vanuatu Viet Nam 0.31 4.00 4.07 0.50 2.30 4.80 3.00 1.50 10.70 0.33 7.00 3.60 1.70 0.54 1.00 1.00 6.10 61 1 002 Ha Noi, etc. 22 4 091 Blood donors General population General population General population 1993 publication 1991 publication 1991 publication 1994 publication 12 180 35 18 11 1 1 542 385 363 66 Kuala Lumpur General population General population Blood donors General population General population Blood donors General population 1985 1991 1993 publication 1988–1991 1996 publication 1993 publication 1993 publication No. positive 299 6 86 No. examined 94 970 154 2 112 Location Sydney Takeo Guangxi Province Sample Blood donors General population General population Year 1990–1991 1990–1991 1996 publication
Source for HBsAg prevalence: Regional Office Computerized EPI Information System. Source for HCV data: WHO Headquarters database 14 November 1997.
Table 3. Characteristics of types of hepatitis Type of hepatitis A B C D E G TT Mode of transmission Fecal/oral - food/waterborne Bloodborne - sexual - perinatal Primarily bloodborne - sexual and perinatal Bloodborne - sexual - perinatal Fecal/oral – waterborne Bloodborne Bloodborne Vaccine Yes Yes No No No No No
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2. PROGRESS IN CONTROL OF VIRAL HEPATITIS 2.1 Immunization against hepatitis B In 1991 the Global Advisory Group of the Expanded Programme on Immunization called for all countries to add hepatitis B vaccine to their national immunization programmes. This
recommendation was endorsed by the World Health Assembly in 1992, and the Health Assembly set disease reduction targets in 1994. These called for an 80% reduction in carrier rates in children by the year 2001. The limited availability of hepatitis B vaccine for national immunization programmes, largely due to cost, has been an obstacle to achieving this goal. Nevertheless, 34 out of 37 countries and areas of the Region are using the vaccine in their national immunization programmes, and all but four countries and areas have a policy of universal infant immunization. Table 4 summarizes vaccine supply in 1998. In general, the vaccine supply situation is reasonable in the medium term. Of the large countries with high carrier rates, China is rapidly approaching full self-sufficiency in vaccine supply through production, and the Philippines is gradually approaching 100% of requirements through purchase. Viet Nam is introducing the vaccine gradually as production levels increase. However, Cambodia and the Lao People’ s Democratic Republic
currently have no supply of vaccine. The situation for smaller countries is currently good. Several Pacific island countries and areas have adequate supplies through reliable funding sources. In 1996 a joint Pacific Regional hepatitis B control project in 10 Pacific island countries, supported by UNICEF, WHO and the Governments of Australia and New Zealand, was established. This project is meeting vaccine requirements in full for three years (1996–1998) and partially for a further two years (1999–2000) while countries phase in national budgets for vaccine purchase (as was done for other vaccines in the Expanded Programme on Immunization). Where adequate supplies of vaccine are available, hepatitis B immunization has been successfully integrated into national immunization programmes. For 1997, 19 countries and areas reported that hepatitis B immunization coverage of infants was over 80%, compared with 17 in 1995, 9 in 1994 and just 3 in 1992 (Table 1).
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Table 4. Vaccine supply and self-sufficiency, hepatitis B vaccine Country/area Hepatitis B vaccine self-sufficient 1992 American Samoa Australia Brunei Darussalam Cambodia China Cook Islands Fiji French Polynesia Guam Hong Kong, China Japan Kiribati Lao People’ s Democratic Republic Macao Malaysia Marshall Islands Micronesia, Federated States of Mongolia Nauru New Caledonia New Zealand Niue Northern Mariana Islands Palau Papua New Guinea Philippines Republic of Korea Samoa Singapore Solomon Islands Tokelau Tonga Tuvalu Vanuatu Viet Nam Wallis and Futuna yes yes yes n.a. yes no no yes yes yes yes no n.a. yes yes no no no no yes yes no no no partial partial yes no yes no no no no no no yes 1998 yes yes yes no no no no yes yes yes yes no no yes yes yes yes no yes yes yes no yes yes partial mostly yes no yes no no no no no partial yes yes yes yes no no yes yes yes yes yes yes yes no yes yes yes yes yes yes yes yes yes yes yes partial mostly yes yes yes yes yes yes yes yes partial yes Purchase Purchase Purchase NA Local production Partner agency Partner agency Purchase Purchase Purchase Local production Partner agency NA Purchase Purchase Purchase Purchase Partner agency Purchase Purchase Purchase Partner agency Purchase Purchase Partner agency, purchase purchase Local production, purchase Partner agency purchase Partner agency Partner agency Partner agency Partner agency Partner agency Local production purchase Adequate supply 1998 Vaccine source
Evaluations of the impact of hepatitis B immunization have been conducted in Australia, China, Japan and in some Pacific island countries. These evaluations have documented significant reductions in chronic carrier rates, typically to below 2% in immunized age groups. In China, the prevalence of HBsAg in children in Shanghai and Beijing was reported to have decreased from 10% to
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1% following the introduction of hepatitis B vaccine. An evaluation of the impact of hepatitis B immunization in four Pacific island countries has recently been conducted. It demonstrated a
significant reduction in the risk of immunized children becoming chronic carriers. The evaluation also showed high levels of protection (80%-86%) against transmission from infectious carrier mothers to their children.
2.2
Blood safety and the control of hepatitis B and C Most industrialized countries have achieved a high level of hepatitis B and C control in recent
years. In these countries blood safety is now well regulated and decreases in transfusion-related hepatitis have been observed. However, despite some notable improvements, blood safety is not
optimal in most developing countries. All countries and areas in the Western Pacific Region test for Hepatitis B surface antigen either before or after donation. Blood donations are screened for hepatitis C virus (HCV) antibodies in all the larger countries of the Western Pacific Region except the Lao People’ s Democratic Republic. French Polynesia, Nauru, Niue, New Caledonia and Papua New Guinea are the only Pacific island countries and areas to screen for hepatitis C. The screening test for hepatitis C is currently expensive and this explains why not all countries routinely screen for HCV. There remains a need for a sensitive, specific, simple, affordable and cost-effective test for hepatitis C that can be used in resource-limited countries. The target of 100% voluntary unpaid and regular donors has been reached in Australia; Hong Kong, China; Japan; Malaysia; New Zealand; the Republic of Korea; and Singapore. However, most countries and areas still pay blood donors. In the Philippines, the phasing out of commercial blood banks has progressed well during the last 12 months, and in China a “Blood Donation” law was passed on 1 October 1998 forbidding payment to blood donors.
2.3
Hepatitis B and C transmission among injecting drug users Hepatitis B and C can both be transmitted through blood and use of contaminated needles is an
important mode of transmission. For this reason, hepatitis C, which is primarily spread through bloodborne transmission, can infect large numbers of injecting drug users (IDUs). In Australia, hepatitis C prevalence among IDUs is estimated to be between 60% and 80%. Some estimates of hepatitis C prevalence among IDUs in Thailand are as high as 90%. Unfortunately,
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hepatitis C prevalence data from many Member States of the Region are lacking. However, it is likely that many countries have similar prevalence rates to those in Australia and Thailand. Although
hepatitis B prevalence is typically lower than hepatitis C prevalence, it also constitutes a serious health problem among IDUs.
2.4
Clinical treatment Currently there are no general protocols providing guidelines on diagnosis, clinical management
and treatment of patients with viral hepatitis or subsequent chronic liver disease. The existing clinical practices for management of patients with acute hepatitis, chronic hepatitis, cirrhosis, and hepatocellular carcinoma are not standardized. In recent years antiviral drugs (interferon, lamivudine, and ribavirin), anti-inflammatory drugs, vaccine therapy, and certain traditional medicines have all been used to treat patients with chronic hepatitis due to HBV and HCV, with variable success. Further studies are needed to identify the most appropriate treatments for patients with chronic hepatitis, before their widespread use can be encouraged.
3. FUTURE
In December 1998 a meeting of the Western Pacific Region Working Group on Viral Hepatitis reviewed the current situation of viral hepatitis and identified priorities for action. The Working Group recommended that the following priority areas be addressed.
3.1
Continued promotion of immunization for Hepatitis B control WHO should concentrate on ensuring the achievement and maintenance of high immunization
coverage in all countries and areas of the Region. This would include facilitating introduction of hepatitis B vaccine in Cambodia and the Lao People’ s Democratic Republic. Attention should be paid to sustaining vaccine supply for countries dependent on partner agency sources. Although 11 countries dependent on partner agencies currently have adequate vaccine supplies, in the longer term these supplies must be sustained by national funds.
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3.2
Improvement of blood safety In order to improve blood safety, WHO should continue to focus not only on screening and
quality assurance in laboratories, but on all the steps in the transfusion chain between the donor and the recipient. Governments should be encouraged to support their own national blood programmes to operate well-organized and cost-effective blood services and to regulate all the activities related to the use of human blood. This would include collecting blood only from voluntary and non-remunerated donors, establishing self-sufficiency, using blood and plasma derivatives effectively and reducing the number of unnecessary transfusions. Through its network of collaborating centres, WHO should work together with countries to identify and characterize serum panels and standardized reagents for the licensing of screening tests that are appropriate for each country's situation.
3.3
Continued monitoring of the epidemiological situation of viral hepatitis The epidemiological situation of viral hepatitis should continue to be closely monitored, not just
for hepatitis B and C but also for hepatitis A and E and other, newly emerging, hepatitis viruses. This information would be used for planning at national and regional levels to address viral hepatitis control issues.