Report of the Hepatitis B Working Group

Canadian Medical Association Journal 1994; 151: 1294-1297
Health Canada, 1994
Reproduced with permission of the Minister of Supply and Services Canada, 1996
Copies of the original report (Canada Communicable Disease Report 1994; 20: 105-112) can be obtained from Eleanor Paulson, editor, CCDR, Bureau of Communicable Disease Epidemiology, Laboratory Centre for Disease Control, Tunney's Pasture, Ottawa, ON K1A 0L2.
The following has been endorsed by the Advisory Committee on Epidemiology (ACE), the National Advisory Committee on Immunization (NACI) and the Executive Board of the Canadian Paediatric Society (CPS).

The Working Group recommends that all jurisdictions in Canada implement a universal hepatitis B vaccination program for children 9 to 13 years of age as soon as resources permit.


Contents


Background

NACI, CPS, a Parliamentary Standing Committee and several other advisory bodies and agencies have recommended that hepatitis B vaccination be added to routine childhood vaccination programs in Canada. The Immunization Practices Advisory Committee of the US Public Health Service and the American Academy of Pediatrics made similar recommendations in 1991; these recommendations have not yet been fully implemented.

Epidemiologic information on hepatitis B in Canada is limited, and there were several issues, including vaccine cost and the most appropriate age for immunization, that required further consideration before any detailed recommendations could be made. Therefore, a working group was established in June 1992 to develop recommendations for the control of hepatitis B in Canada, including options for universal immunization programs.

The working group had representation from ACE, NACI, the Laboratory Centre for Disease Control (LCDC) and CPS.

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Introduction

Since the discovery of the hepatitis B virus (HBV) by Baruch, Blumberg and colleagues in the 1960s, researchers have accumulated a wealth of information concerning the virologic, epidemiologic and immunologic aspects, clinical characteristics and laboratory diagnosis of HBV infection. Despite the availability of effective and safe vaccines in Canada since 1982, the reported incidence of acute hepatitis and of death from HBV infections increased progressively during the 1980s.[1] This increase reflects a failure of a selective vaccination strategy directed at identifiable high-risk groups to control virus transmission in the population. Health care workers are the one exception to this statement. Implementation of vaccination policies in hospitals has greatly reduced the incidence of acute HBV infection in health care workers,[2] but this group has never accounted for a substantial proportion of cases in Canada.

There are many reasons for the failure of the present selective immunization strategy to affect disease incidence: cost of the vaccine, lack of physician awareness, difficulties in reaching members of high-risk groups, who often do not perceive themselves as being at risk, concerns about vaccine safety, lack of compliance in completing vaccination schedules and the absence of identified risk factors in 30% to 60% of recently infected individuals.

For these reasons NACI endorsed the principle of universal vaccination in 1991,[3] and the CPS supported implementation of universal vaccination against HBV in 1992.[4] British Columbia has recently successfully introduced a universal preadolescent vaccination program.

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Epidemiology

Reported rates of HBV infection in Canada increased more than twofold from 1980 to 1990, with a peak incidence reported in 1989.[5] Although this increase may represent, in part, increased physician and patient awareness to test for the disease or more complete reporting of cases, it occurred despite selective (high-risk) hepatitis B vaccination programs that began in 1982. Provincial and territorial rates varied markedly, from 0.8 to 29.2 per 100 000 in 1990, and not all provinces experienced increases. Even in those provinces that experienced declining or stable rates of HBV infection during this period, incidence continued to be of concern.

No obvious risk factors are recorded for 30% to 60% of cases reported. In addition, even when risk factors are present, physicians may not identify the risk and need for vaccination in a large proportion of such cases. Finally, targeted programs can usually identify candidates for vaccination only after the risk behaviour has begun. Thus, the failure of a selective vaccination strategy alone to eliminate HBV infection could be predicted.

Less than 3% of reported cases of acute HBV infection occur in children. The prevalence of unrecognized acute and chronic infection in children in Canada is unknown but believed to be low except in readily identified risk groups. Incidence increases dramatically in the 15- to 19-year age group and peaks in the 20- to 40-year age group, suggesting that sexual transmission and, possibly, injection drug use are major factors for HBV infection in Canada.

For maximum impact, therefore, vaccination should ideally begin before 15 years of age (before incidence begins to rise) but not necessarily early in childhood, since risk in younger children seems to be confined to small, well-defined groups, such as infants born to HBV-infected mothers, for whom prevention programs already exist. Since risk cannot be predicted for a substantial proportion of cases, universal coverage is required.

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Vaccination dosage and schedules

NACI has recently published a comprehensive statement on hepatitis B vaccines.[6] Three doses of vaccine reliably induce protective immunity in more than 90% of healthy individuals with 99% seroconversion in persons 2 to 19 years of age. In British Columbia, a 97% seroconversion rate was documented in grade 6 students. Protection appears to be of long duration even if antibody levels decline or become undetectable. Young children (10 years or under) respond to smaller doses than do adults; adolescents may also require smaller doses (depending on the product used). Whether young adolescents would respond to lower doses is being investigated.

While an optimal schedule appears to be doses at 0, 1 and 6 months, virtually all schedules tested appear to result in satisfactory seroconversion rates and antibody levels, allowing considerable flexibility in designing vaccination programs.

The need for booster doses after receiving a primary series has not been established. Protection against clinical disease and the carrier state has been documented to persist for at least 10 years. Whether booster doses may be required after 15 to 25 years following primary vaccination will not be known for many years. This theoretical concern is particularly important if an infant vaccination program is chosen but could also be a consideration for vaccination of older groups.

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Options

The Working Group considered four options and developed pros and cons for each one (Appendix 1). These options were as follows: (a) status quo (i.e., selective vaccination of high-risk individuals), (b) universal infant vaccination, (c) universal vaccination of adolescents (i.e., 14 to 18 years of age), and (d) universal vaccination of children 9 to 13 years of age. (The exact age limits for this group were difficult to define, as was a term to describe them. "Preadolescent" was the most commonly used term, but it was not felt to be adequate, particularly if 12- and 13-year-olds are included.) Continuation of universal prenatal screening, provision of hepatitis B immune globulin (HBIG) and vaccine to newborns of carrier mothers, and continued vaccination of children at high risk would be recommended under all strategies. (It is estimated that early childhood infections account for up to 35% of all carriers; 90% or more of these cases could be prevented by such programs.) Continued and improved selective vaccination of adults at risk would also be required for the foreseeable future. (A fifth option of physician delivery of vaccine to children, with parents paying the cost, was not considered in any detail by the Working Group because it would not achieve control of HBV infection. However, this possibility is briefly mentioned in the recommendations.)

The Working Group was given access to the planning document used in British Columbia to develop and justify its program as well as a cost-benefit analysis prepared by Krahn and Detsky for LCDC. The former was difficult to generalize to the whole of Canada, and the latter would require considerable updating and additional detail before it could be used. The most useful assessment of cost-effectiveness was found to be an analysis by Bloom and associates[6] that concluded that optimal cost-effectiveness is achieved with a strategy of prenatal screening and vaccination of exposed newborns combined with routine administration of vaccine to 10-year-old children.

The Working Group was impressed with the success of the BC grade-6 hepatitis-B vaccination program. Well over 90% of eligible children accepted vaccination, and 92% completed a three-dose series. Reports of adverse reactions were minimal. It was concluded that a program aimed at this age group was feasible and affordable but that it could only be successful if delivered as a school-based program conducted exclusively by the public health system.

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Recommendations

  1. Canada should adopt a long-term national goal of elimination of acute HBV infection and develop specific targets for incidence reduction for the years 2000, 2005 and 2010.

  2. To achieve this goal, all jurisdictions should do the following, as soon as possible.

    (a) Introduce universal childhood hepatitis B vaccination as part of routine vaccination schedules. This vaccine should be administered:

    (b) Continue prenatal screening of all pregnant women for hepatitis B surface antigen (HBsAg). Infants born to HBsAg-positive mothers should receive HBIG as soon as possible after birth followed by three doses of hepatitis B vaccine. Postvaccination serologic testing should be done to assure that protection has been achieved. Public health authorities should monitor these screening and vaccination programs to ensure that they are achieving their goals.

  3. Targeted programs for persons at high risk of exposure to hepatitis B (as defined by NACI) should be continued and improved. This is particularly important in the period before universal childhood vaccination is implemented in all jurisdictions, but it will also be necessary for the foreseeable future until those vaccinated under a universal program reach middle age.

  4. Until universal programs are instituted, physicians may wish to offer vaccine to children at cost. This would not achieve control of HBV infection but could offer individual protection to those who receive it. The age at which vaccine should be offered is unclear. Infants are easier to reach but, apart from those at high risk (infants born to HBsAg-positive mothers, members of the household of a carrier and children of parents from high-risk countries), for whom vaccine is already recommended, there is no advantage for the patient in being vaccinated in infancy rather than at a later age, nearer the time of risk. Any cost advantage of smaller doses for those under 11 years is limited to situations where more than one child can be vaccinated at the same time.

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References

  1. Delage G, Carter AO: Hepatitis B infection in Canada. Epidemiology and implications for control. Can Fam Physician 1992; 38: 2656-2666
  2. Alter MJ, Hadler SC, Margolis HS et al: The changing epidemiology of hepatitis B in the United States. JAMA 1990; 263: 1218-1222
  3. Statement on universal immunization against hepatitis B. Can Dis Wkly Rep 1991; 17: 165
  4. Infectious Diseases and Immunization Committee, Canadian Paediatric Society: Hepatitis B in Canada: the case for universal immunization. CMAJ 1992; 146: 25-28
  5. National Advisory Committee on Immunization: Hepatitis B vaccine. In Canadian Immunization Guide, 4th ed, [cat no H49-8/1993E], Health Canada, Ottawa, 1993: 46-57
  6. Bloom BS, Hellman AL, Fendrick AM et al: A reappraisal of hepatitis B virus vaccination strategies using cost-effectiveness analysis. Ann Intern Med 1993; 118: 298-306

Source: Working Group: Drs. J. Carlson (ACE), F. Stratton (ACE), G. Delage (CPS), S. Tamblyn (NACI), D. Holton (LCDC), L. Tyrrell (NACI), V. Marchessault (CPS); J. Waters (chair; NACI/ACE), A. Bell (provincial epidemiologist, British Columbia -- consultant to the working group) and Ms. S. Ladouceur (LCDC -- administrative support).


Disclaimer

This guideline is for reference and education only and is not intended to be a substitute for the advice of an appropriate health care professional or for independent research and judgement. The CMA relies on the source of the CPG to provide updates and to notify us if the guideline becomes outdated. The CMA assumes no responsibility or liability arising from any outdated information or from any error in or omission from the guideline or from the use of any information contained in it.
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