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Vaccines for the 21st Century: A Tool for Decisionmaking APPENDIX 3 Coccidioides immitis DISEASE BURDEN Epidemiology For the purposes of the calculations in this report, the committee estimated that there are 100,000 new cases of C. immitis infection each year in the United States. C. immitis infections are most prominent in several geographic locations in the United States, primarily California, Texas, New Mexico, Arizona, Nevada. The committee estimated that half of new infections occur to people born in those regions and half occur to people who have migrated into those regions. This distinction has significant implications in other portions of the modeling exercise. The highest incidence was estimated to occur in people between the ages of 15 and 44 years of age. Table A3–1 shows the age distribution of incidence and mortality associated with C. immitis. The committee estimated that males and females are equally vulnerable to coccidioides infection. The committee estimated there are 117 deaths per year associated with the infection. The treatment of HIV infection and AIDS and the effect of those changes on the health status and costs of care experienced by those with HIV has changed rapidly in recent years and is expected to continue to do so. Therefore, the committee has chosen not to include a scenario specific to infection in those See Appendix 28 for more information.
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Vaccines for the 21st Century: A Tool for Decisionmaking Table A3–1 Incidence and Mortality Rates for Coccidioides 5-year Age Groups Total Population Incidence Rates (per 100,000) (5-year age groups) Cases 0–4 20,182,000 0.00 0 5–9 19,117,000 0.00 0 10–14 18,939,000 57.73 10,934 15–19 17,790,000 57.73 10,270 20–24 18,473,000 57.73 10,665 25–29 19,294,000 57.73 11,139 30–34 22,376,000 57.73 12,918 35–39 22,215,000 57.73 12,825 40–44 19,934,000 57.73 11,508 45–49 16,873,000 57.73 9,741 50–54 13,351,000 14.65 1,956 55–59 11,050,000 14.65 1,619 60–64 10,191,000 14.65 1,493 65–69 10,099,000 14.65 1,480 70–74 8,865,000 14.65 1,299 75–79 6,669,000 14.65 977 80–84 4,419,000 14.65 648 85+ 3,598,000 14.65 527 Total 263,435,000 100,000 Age Groups Population Mortality Rates (per 100,000) % Distribution of Deaths <1 3,963,000 0.000 0.000 1–4 16,219,000 0.000 0.000 5–14 38,056,000 0.003 0.009 15–24 36,263,000 0.019 0.058 25–34 41,670,000 0.039 0.139 35–44 42,149,000 0.030 0.109 45–54 30,224,000 0.054 0.139 55–64 21,241,000 0.064 0.115 65–74 18,964,000 0.148 0.239 75–84 11,088,000 0.147 0.139 85+ 3,598,000 0.181 0.055 Total 263,435,000 0.045 1.0000 with HIV/AIDS. Consideration of this population would result in differences in the calculations achieved with this model, but the uncertainties associated with doing so were thought to be quite extreme.
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Vaccines for the 21st Century: A Tool for Decisionmaking Disease Scenarios For the purposes of the calculations in this report, the committee estimated that 40% of all C. immitis infections were asymptomatic. Symptomatic infections manifested as mild respiratory illness with and without complications of erethyma nodosum, pneumonia, and as a persistent, disseminated infection. The health utility indices associated with C. immitis infection vary from .65 for hospitalization with disseminated infection to .90 for the prolonged outpatient phase of a persistent, disseminated infection. Table A3–2 illustrates the estimated number of cases in each health state, the duration of time that state is experienced, and the health utility index (HUI) associated with each state. COST INCURRED BY DISEASE Table A3–3 summarizes the health care costs incurred by C. immitis infections. For the purposes of the calculations used in this report, it was assumed that the mild respiratory illness associated with C. immitis infection leads to the costs of a limited physician visit and that only half of those with this illness would seek medical attention. It is assumed that 100% of people with more severe complications seek medical attention. Those people with complications of erythema incur costs associated with the respiratory illness (limited physician visit, diagnostic, medication) and several specialist visits for assessment and treatment of the complications. Outpatient pneumonia is assumed to be associated with physician visits, diagnostics, and medications. Inpatient hospital costs were included for the few patients who were assumed to require it. Persistent/disseminated infection was associated with several hospitalizations as well as numerous outpatient visits, diagnostics, and medications over a 3-year period. Although the health care scenarios are the same for those who would be immunized in infancy and as migrants (at older ages), the costs are calculated separately to allow for the effects of discounting, which will be different in infants (who might have a lag of many years until disease manifestations) and in migrants (some of whom will have much less of a lag between immunization and prevention of disease and the associated health care costs). VACCINE DEVELOPMENT The committee estimated that development is feasible but is not imminent. The estimates are that it will take 15 years until licensing and that $360 million needs to be invested.
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Vaccines for the 21st Century: A Tool for Decisionmaking Table A3–2 Morbidity Scenarios for Coccidioides Infection No. of Cases % of Cases Committee HUI Values Duration Total Deaths 117 Total Cases (new symptomatic and asymptomatic infections) 100,000 No Symptoms 40% 1.00 Mild respiratory illness 17% 0.81 0.0192 (1 week) Mild respiratory illness with erythema complications 3% mild respiratory illness 0.81 0.0192 (1 week) erythema nodosum/toxic erythema/arthritis 0.75 0.0575 (3 weeks) Pneumonia: outpatient only 30% 0.75 0.0575 (3 weeks) Pneumonia 5% self-limiting: inpatient 0.73 0.0192 (1 week) self-limiting: outpatient 0.75 0.0575 (3 weeks) Persistent/disseminated 5% P/D: inpatient 0.65 0.0384 (2 weeks) P/D: outpatient: 3-year period 0.90 3.0000 (3 years) Table A3–3 Health Care Costs Associated with Coccidioides Infection % with Care Cost per Unit Units per Case Form of Treatment Mild respiratory illness 50% $50 1.0 physician a Mild respiratory illness with erythema complications mild respiratory illness 100% $50 3.0 physician a, diagnostic a, medication b erythema nodosum/toxic erythema/arthritis 100% $100 2.0 physician b Pneumonia: outpatient only 100% $250 1.0 outpatient treatment (physician a and b, diagnostic a, medication b) Pneumonia self-limiting: inpatient 100% $4,000 1.0 inpatient treatment self-limiting: outpatient 100% $250 1.0 outpatient treatment (e.g., physician a and b, medication b, diagnostic a) Persistent/disseminated P/D: Inpatient 100% $4,000 2.0 inpatient treatment P/D: outpatient: 3 -year period 100% $50 7.0 outpatient treatment (physician a, diagnostic a, medication b)
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Vaccines for the 21st Century: A Tool for Decisionmaking VACCINE PROGRAM CONSIDERATIONS Target Population The target population for this vaccine is approximately 1,035,300 people: all infants born in the geographic regions identified above and migrants into the area. The model assumes that half of immigrants into the area from the western part of the United States would not have had the vaccine already. For the purposes of the model, the average age for migrants into the area is estimated to be 27.9 years, and immunization is estimated to occur within 1 year of migration. The committee estimated that 90% of infants would receive the vaccine, compared with only 10% of migrants. Vaccine Schedule, Efficacy, and Costs The committee estimated that this would be a relatively low-cost vaccine, costing $50 per dose. Vaccine administration would cost an additional $10. The committee has accepted default assumptions for this vaccine that it will require a series of 3 doses and that efficacy will be 75%. Table 4–1 summarizes vaccine program assumptions for all vaccines considered in this report. RESULTS If a vaccine program for c.immitis 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 1,700. 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 240. If a vaccine program for c.immitis 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 $44.8 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 health care costs saved would be $6.3 million. If a vaccine program for c.immitis 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 $190 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 $53.4 million.
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Vaccines for the 21st Century: A Tool for Decisionmaking Using committee assumptions of time and costs until licensure, the fixed cost of vaccine development has been amortized and is $10.8 million for a C. immitis 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 $85,000. 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 $240,000. See Chapters 4 and 5 for details on the methods and assumptions used by the committee for the results reported. READING LIST Byerly E, Deardorff K. National and State Population Estimates: 1990 to 1994, U.S. Bureau of the Census, Current Population Reports, pp. 25–1127, U.S. Government Printing Office, Washington, DC, 1995. California Department of Finance. Population of California Counties and the State and Components of Change [WWW document]. URL http://library.ca.gov/california/4e2tabl.html (accessed January 24, 1997). CDC. Compressed Mortality Database. WONDER (wonder.cdc.gov). 1997. ICD-9, Number 114. Dugger KO, Villareal KM, et al. Cloning and Sequence Analysis of the cDNA for a Protein from C.immitis with Immunogenic Potential. Biochemical and Biophysical Research Communications 1996; 218:485. Galgiani JN, Catanzaro A, Cloud GA, et al. Fluconazole Therapy for Coccidioidal meningitis—The NIAID—Mycoses Study Group. Annals of Internal Medicine 1993; 19:28–35. Hansen KA. Geographical Mobility: March 1993 to March 1994, U.S. Bureau of the Census, Current Population Reports, pp. 20–485, U.S. Government Printing Office, Washington, DC, 1995. Kirkland TN, Fierer J. Coccidioidomycosis: a Reemerging Infectious Disease. Emerging Infectious Diseases 1996; 2:192–9. Libke RD, Granoff DM. Coccidioidomycosis. In: Textbook of Pediatric Infectious Diseases. RD Feigin and JD Cherry eds. Philadelphia, PA: WB Saunder Company, 1992, pp. 1916–1928. Pappagianis D. Evaluation of the Protective Efficacy of the Killed C.immitis Spherule Vaccine in Humans. American Review of Respiratory Disease 1993; 148:656–660. Pappagianis D. Marked Increase in Cases of Coccidioidomycosis in California: 1991, 1992, and 1993. Clinical Infectious Diseases 1994; 19(Suppl 1):S14–8. Stevens DA. C.immitis. In: Principles and Practice of Infectious Diseases. GL Mandell, JE Bennett, R Dolin, eds. New York, NY: Churchill Livingstone, 1995, pp. 2365–2374. Texas Agricultural Experiment Station, Department of Rural Sociology. 1994 Total Population Estimates for Texas Counties [WWW document]. URL http://www-txsdc.tamu.edu/txpop94.html (accessed February 13, 1997). Texas Department of Health. Bureau of Vital Statistics Annual Report 1994.
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