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APPENDIX 13
Insulin-Dependent Diabetes Mellitus

Insulin-dependent diabetes mellitus (IDDM) is becoming one of the most studied autoimmune diseases. The pathogenesis of IDDM involves a sequence of events ultimately leading to the destruction of beta cells of the pancreas which normally function as the insulin-producing cells. First, there must be a genetic susceptibility to the disease. Next, an environmental event, possibly a virus, initiates the disease process. Once the disease has been triggered, an inflammatory response called “insulitis” begins in the pancreas. Insulitis is an inflammatory infiltrate composed mainly of T lymphocytes which invade the cells of the pancreas. The fourth step is a transformation in the surface of the beta cells causing the activation of the autoimmune response. This response occurs because the beta cell is no longer recognized as “self” but is targeted as a “nonself” foreign cell. As a result, the beta cells are destroyed, which leads to the appearance of diabetes mellitus.

DISEASE BURDEN

Epidemiology

For the purposes of the calculations in this report, the committee estimated that there are approximately 30,000 new cases of insulin-dependent diabetes mellitus (IDDM) each year in the United States. It was assumed that the incidence varies slightly with age, but that the highest incidence occurs in people between 5 and 34 years of age.



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Vaccines for the 21st Century: A Tool for Decisionmaking APPENDIX 13 Insulin-Dependent Diabetes Mellitus Insulin-dependent diabetes mellitus (IDDM) is becoming one of the most studied autoimmune diseases. The pathogenesis of IDDM involves a sequence of events ultimately leading to the destruction of beta cells of the pancreas which normally function as the insulin-producing cells. First, there must be a genetic susceptibility to the disease. Next, an environmental event, possibly a virus, initiates the disease process. Once the disease has been triggered, an inflammatory response called “insulitis” begins in the pancreas. Insulitis is an inflammatory infiltrate composed mainly of T lymphocytes which invade the cells of the pancreas. The fourth step is a transformation in the surface of the beta cells causing the activation of the autoimmune response. This response occurs because the beta cell is no longer recognized as “self” but is targeted as a “nonself” foreign cell. As a result, the beta cells are destroyed, which leads to the appearance of diabetes mellitus. DISEASE BURDEN Epidemiology For the purposes of the calculations in this report, the committee estimated that there are approximately 30,000 new cases of insulin-dependent diabetes mellitus (IDDM) each year in the United States. It was assumed that the incidence varies slightly with age, but that the highest incidence occurs in people between 5 and 34 years of age.

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Vaccines for the 21st Century: A Tool for Decisionmaking Disease Scenarios For the purposes of the calculation in this report, the committee assumed that there are two phases of health states associated with IDDM. During the first 20 years, it is assumed that on average, patients experience minor discomforts and only occasional, serious health incidents. This phase was assumed to be associated with a health utility index (HUI) of .97. During the second phase, which lasts for the duration of the person’s life, there are many possible complications with varying impacts on a HUI. On average, it was assumed that this phase was associated with an HUI of .79. It was assumed that patients with IDDM, on average, experience a decrease in life expectancy of approximately 12 years. This was calculated as one-third reduction of life expectancy at the time of onset of the disease. COST INCURRED BY DISEASE Table A13–1 summarizes the health care costs incurred by IDDM. For the purposes of the calculations in this report, it was assumed that 70% of patients receive conventional treatment for IDDM and 30% receive intensive treatment. It is assumed that there are costs associated with the diagnostic and very early phase of treatment, with the disease management during the 20-year period that was assumed to be free of chronic, serious sequelae, and with the disease management during the second phase, as well as costs associated with serious complications. It will be assumed that a therapeutic vaccine strategy will only reduce costs associated with long-term management of disease and treatment of complications. The initial diagnostic phase will not be eliminated. Therefore, only the preventable costs will be described in detail. Costs incurred during the first 20 years of disease management include outpatient visits to specialists (endocrinologists and ophthalmologists, for example) and associated diagnostics, occasional visits to diabetes case managers/educators, and treatment for severe hypoglycemia in some patients. Self-care supplies are assumed to include insulin, syringes, and blood glucose monitoring supplies. It is assumed that patients in intensive treatment incur higher costs due to more frequent physician visits, diagnostics, and supplies. Costs incurred due to serious complications associated with IDDM are also approximated for the calculations in the report. For example, it was assumed that 60% of people with IDDM will require treatment for retinopathy, renal evaluation and angiotensin-converting enzyme-inhibitor medication, and neurologic evaluation. It is assumed that 20% incur additional costs associated with blindness and end-stage renal disease. It was also assumed that a small percentage of patients will require amputation and associated costs. The committee assumed that it will take 15 years until licensure of a therapeutic IDDM vaccine and that $360 million needs to be invested. Table 4–1

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Vaccines for the 21st Century: A Tool for Decisionmaking summarizes vaccine development assumptions for all vaccines considered in this report. For the purposes of the calculations in this report, it is assumed that the costs associated with diagnostic phase would be incurred even with a treatment vaccine strategy. Therefore, only the costs of the treatment phase will be assumed to be averted with a vaccine strategy. VACCINE DEVELOPMENT The committee assumed that it will take 15 years until licensure of a therapeutic IDDM vaccine and that $360 million needs to be invested. Table 4–1 summarizes vaccine development assumptions for all vaccines considered in this report. VACCINE PROGRAM CONSIDERATIONS Target Population For the purposes of the calculations in this report, it is assumed that the target population for this vaccine is all newly diagnosed cases of IDDM. It was assumed that 90% of the target population would utilize the vaccine. Vaccine Schedule, Efficacy, and Costs For the purposes of the calculations in this report, it was estimated that this vaccine would cost $500 per dose and that administration costs would be $10 per dose. Default assumptions for therapeutic vaccines of a 3-dose series and 40% effectiveness were accepted. Table 4–1 summarizes vaccine program assumptions for all vaccines considered in this report. RESULTS If a vaccine program for IDDM were implemented today and the vaccine was 100% efficacious and utilized by 100% of the target population, the annualized present value of the QALYs gained would be 170,000. Using committee assumptions of less-than-ideal efficacy and utilization and including time and monetary costs until a vaccine program is implemented, the annualized present value of the QALYs gained would be 38,000.

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Vaccines for the 21st Century: A Tool for Decisionmaking Table A13–1 Health Care Costs Associated with IDDM   % of Cases Duration (years) % with Care Cost per Unit Units per Case Form of Treatment First 20 years 100%   CONVENTIONAL THERAPY—70% Treatment phase Yearly Hypoglycemia 20.00 20% $500 1.0 Treatment of severe hypoglycemia   20.00 35% $100 1.0 Treatment modification Physician visits and diagnostics 20.00 35% $150 4.0 Quarterly visit plus diagnostic     20.00 35% $150 2.0 Semiannual visit plus diagnostic 20.00 35% $150 1.0 Specialist visit plus diagnostic 20.00 35% $50 1.0 Case management, counseling Self-management 20.00 70% $15 18.0 Insulin   20.00 70% $100 12.0 Other supplies INTENSIVE THERAPY—30% Treatment phase Yearly Hypoglycemia 20.00 15% $500 1.0 Treatment of severe hypoglycemia Physician visits and diagnostics 20.00 30% $150 1.0 Quarterly visit (endocrinologist)     20.00 30% $500 1.0 Annual visit (e.g., ophthalmologist) 20.00 30% $50 2.0 Case management, counseling Self-management 20.00 30% $16 24.0 Insulin   20.00 30% $200 12.0 Other supplies Remainder of life 100%  

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Vaccines for the 21st Century: A Tool for Decisionmaking CONVENTIONAL THERAPY Hypoglycemia 15.00 15% $500 1.0 Treatment of severe hypoglycemia   15.00 5% $220 1.0 Treatment modification Physician visits and diagnostics 15.00 70% $80 2.0 Quarterly visit   15.00 70% $100 1.0 Semiannual visit 15.00 70% $250 1.0 Annual visit 15.00 70% $50 1.0 Case management, counseling Self-management 15.00 70% $16 24.0 Insulin INTENSIVE THERAPY Hypoglycemia 15.00 30% $500 1.0 Treatment of severe hypoglycemia Physician visits and diagnostics 15.00 30% $70 8.0 Monthly visit   15.00 30% $120 2.0 Quarterly visit 15.00 30% $120 1.0 Semiannual visit 15.00 30% $280 1.0 Annual visit 15.00 30% $50 1.0 Case management, counseling Self-management 15.00 30% $16 24.0 Insulin   15.00 30% $2,000 1.0 Other supplies COMPLICATIONS (conventional and intensive treatment) Retinopathy Episodic   60% $950 1.0 Photocoagulation Chronic treatment 7.00 20% $1,900 1 Blindness Nephropathy Episodic   60% $1,100 1.0 Renal evaluation Chronic treatment 7.00 20% $46,000 1 End-stage renal disease treatment (per year) Neuropathy Episodic   60% $125 1.0 Neurologic evaluation   5% $31,225 1.0 Lower extremity amputation

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Vaccines for the 21st Century: A Tool for Decisionmaking If a vaccine program for IDDM were implemented today and the vaccine was 100% efficacious and utilized by 100% of the target population, the annualized present value of the health care costs saved would be $2.5 billion. Using committee assumptions of less-than-ideal efficacy and utilization and including time and monetary costs until a vaccine program is implemented, the annualized present value of the health care costs saved would be $550 million. If a vaccine program for IDDM were implemented today and the vaccine was 100% efficacious and utilized by 100% of the target population, the annualized present value of the program cost would be $45 million. Using committee assumptions of less-than-ideal efficacy and utilization and including time and monetary costs until a vaccine program is implemented, the annualized present value of the program cost would be $25 million. Using committee assumptions of time and costs until licensure, the fixed cost of vaccine development has been amortized and is $10.8 million for an IDDM vaccine. If a vaccine program were implemented today and the vaccine were 100% efficacious and utilized by 100% of the target population, the annualized present value of the cost per QALY gained is -$14,500. A negative value represents a saving in costs in addition to a saving in QALYs. Using committee assumptions of less-than-ideal utilization and including time and monetary costs until a vaccine program is implemented, the annualized present value of the cost per QALY gained is -$13,500. See Chapters 4 and 5 for details on the methods and assumptions used by the committee for the results reported. READING LIST DERI Mortality Study Group. International Analysis of Insulin-Dependent Diabetes Mellitus Mortality: A Preventable Mortality Perspective. American Journal of Epidemiology 1995; 142:612–618. Gorham ED, Garland FC, Barrett-Connor E, et al. Incidence of Insulin-Dependent Diabetes Mellitus in Young Adults: Experience of 1,587,630 US Navy Enlisted Personnel. American Journal of Epidemiology 1993; 138:984–987. Metcalfe MA, Baum JD. Incidence of Insulin-Dependent Diabetes in Children Aged Under 15 years in the British Isles During 1988. BMJ 1991; 302:443–447. Mølbak AG, Christau B, Marner B, et al. Incidence of Insulin-Dependent Diabetes Mellitus in Age Groups Over 30 years in Denmark. Diabetic Medicine 1994; 11:650–655. National Institute of Diabetes and Digestive and Kidney Diseases. Diabetes Statistics [WWW document]. URL http://www.niddk.nih.gov/index.htm (accessed September 23, 1996). Schoenle EJ, Molinari L, Bagot M, et al. Epidemiology of IDDM in Switzerland. Diabetes Care 1994; 17:955–960.