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Vaccines for the 21st Century: A Tool for Decisionmaking
APPENDIX 1
Borrelia burgdorferi
DISEASE BURDEN
Epidemiology
For the purposes of the calculations in this report, the committee estimated that there are 12,000 new cases of infection each year in the United States. The risk of borrelia infection is highest in certain regions of the United States, such as, New England, the Mid-Atlantic states, and certain areas in the Midwest. The committee assumed that within epidemic regions new infections occur equally in males and females and that there are no deaths. The incidence rate is 4.56 per 100,000, but varies slightly by age group. The highest incidence is estimated to occur in the age groups that spend the most amount of time out of doors, that is, those up to 14 years of age. Table A1–1 illustrates the age distribution of new cases of borrelia infection used in the model. Approximately half of all new infections are assumed to occur in people born in the region and half in migrants into the area.
Disease Scenarios
For the purposes of the calculations in this report, the committee assumed that 90% of people newly infected with borrelia experience acute manifestations and seek treatment. The morbidity results in 3 weeks of minor illness associated with a health utility index (HUI) of .89. Another 2% of the new infections experience the same acute illness but do not seek treatment. The committee estimated that 8% of all new infections lead to chronic morbidity expressed as recurrences over a long period of time. The committee estimated that such people experience approximately 2 months per year of illness associated with a HUI of .79 and that
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Table A1–1 Incidence Rates—Borrelia burgdorferi
5-Year Age Groups
Total Population
Incidence Rates (per 100,000) (5-yr age groups)
Cases
Age Groups
Population
Incidence Rates (per 100,00)
0–4
20,182,000
4.95
998
<1
3,963,000
4.95
5–9
19,117,000
4.95
945
1–4
16,219,000
4.95
10–14
18,939,000
4.95
937
5–14
38,056,000
4.95
15–19
17,790,000
4.27
759
15–24
36,263,000
4.27
20–24
18,473,000
4.27
789
25–34
41,670,000
4.27
25–29
19,294,000
4.27
824
35–44
42,149,000
4.88
30–34
22,376,000
4.27
955
45–54
30,224,000
4.61
35–39
22,215,000
4.88
1,084
55–64
21,241,000
4.27
40–44
19,934,000
4.88
973
65–74
18,964,000
4.27
45–49
16,873,000
4.88
823
75–84
11,088,000
4.27
50–54
13,351,000
4.27
570
• 85
3,598,000
4.27
55–59
11,050,000
4.27
472
60–64
10,191,000
4.27
435
Total
263,435,000
4.56
65–69
10,099,000
4.27
431
70–74
8,865,000
4.27
378
75–79
6,669,000
4.27
285
80–84
4,419,000
4.27
189
• 85
3,598,000
4.27
154
Total
263,435,000
12,000
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these recurrences occur for 10 years. Table A1–2 summarizes the disease scenarios associated with borrelia infections.
COST INCURRED BY DISEASE
Health care costs are incurred through diagnostic evaluation, physician visits, and antibiotics. Table A1–3 summarizes the health care costs incurred by borrelia infections. For the purposes of the calculations, it was assumed that all people with acute manifestations incur two physician visits and a prescription antibiotic, and that half receive diagnostic tests. It was assumed that each recurrence is associated with two physician visits and a prescription medication, and that the recurrences occur for 10 years.
VACCINE DEVELOPMENT
The committee assumed that the development of a Borrelia burgdorferi vaccine is feasible and that licensure is imminent (a Borrelia vaccine for use in persons 15 years of age and older was licensed prior to the completion of this report). The estimates for this report are that it will take 3 years until licensure is completed and that $120 million needs to be invested. Table 4–1 summarizes vaccine development assumptions for all vaccines considered in this report.
VACCINE PROGRAM CONSIDERATIONS
Target Population
The committee’s analysis assumes that immunization with this vaccine will occur only in those geographic regions discussed under the epidemiology section. Immunization will occur during infancy or within 1 year of migration to the area. It is estimated that 90% of infants will receive the immunization. The committee estimates that only 10% of migrants into an area will receive the immunization.
Vaccine Schedule, Efficacy, and Costs
The committee estimated that this vaccine would cost $100 per dose. Vaccine administration would cost an additional $10. The committee has accepted default assumptions for this vaccine that estimate 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.
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Table A1–2 Borrelia burgdorferi
No. of Cases
% of Cases
Committee HUI Values
Duration (years)
MORBIDITY SCENARIOS
Total Deaths
0
Total Cases
12,000
I.
Patients who receive treatment
90%
Acute manifestations
0.89
0.0575 (3 weeks)
II.
Untreated patients—no recurrence
2%
Acute manifestations
0.89
0.0575 (3 weeks)
III.
Complications in untreated patients—recurrences
8%
Acute manifestations
0.89
0.0575 (3 weeks)
Recurrences (over 10 years)
0.79
0.1667 (2 months/year over 10 years)
Table A1–3 Health Care Costs—Borrelia burgdorferi
Duration (years)
% with Care
Cost per Case
Cost per Unit
Units per Case (or per year)
Form of Treatment
I.
Patients who receive treatment
Acute manifestations
0.0575
100%
$100
$50
2.0
Physician A
0.0575
100%
$50
$50
1.0
Medication B
0.0575
50%
$100
$100
1.0
Diagnostic B
II.
Complications in untreated patients—recurrences
(2 months per year over 10 years)
10,000
100%
$100
$50
2.0
Physician A
100%
$50
$50
1.0
Medication B per recurrence
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RESULTS
If a vaccine program for B. burgdorferi 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 200. 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 39.
If a vaccine program for B. burgdorferi 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 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 $410,000.
If a vaccine program for B. burgdorferi 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 $690 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 $280 million.
Using committee assumptions of time and costs until licensure, the fixed cost of vaccine development has been amortized and is $3.6 million for a B. burgdorferi 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 $3.5 million. 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 $7.3 million.
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.
CDC. Summary of Notifiable Diseases, United States 1994. Morbidity and Mortality Weekly Report 1994; 43:1–80.
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.
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Stechenberg BW. Borrelia: Lyme Disease. In: Textbook of Pediatric Infectious Diseases. RD Feigin and JD Cherry eds. Philadelphia, PA: WB Saunder Company, 1992, pp. 1062–1067.
Steere AC. Borrelia burgdorferi (Lyme Disease, Lyme Borreliosis). In: Principles and Practice of Infectious Diseases. GL Mandell, JE Bennett, Dolin R eds. New York: Churchill Livingstone, 1995, pp. 2143–2155.
Ventura SJ, Martin JA, Mathews TJ, et al. Advance Report of Final Natality Statistics, 1994. Monthly Vital Statistics Report 1996; 44.
Wormser GP. Prospects for a Vaccine to Prevent Lyme Disease in Humans. Clinical Infectious Diseases 1995; 21:1267–1274.
Representative terms from entire chapter:
target population