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Vaccines for the 21st Century: A Tool for Decisionmaking (2000)

Chapter: Appendix 16: Mycobacterium tuberculosis

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Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
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APPENDIX 16
Mycobacterium tuberculosis

In the majority of infected individuals, the primary lesions of mycobacterium tuberculosis (TB) heal completely and leave no clinical evidence of prior infection except hypersensitivity to tuberculin. In some however, the primary infection progresses directly and evolves into a pneumonic process as the organisms spread through the bronchi or when a tuberculous node ruptures into a bronchus. Contiguous spread can cause infection in the pleural and pericardial spaces. At this stage, pleurisy, which is usually abrupt and resembles bacterial pneumonia with fever, chest pain, and shortness of breath are present.

Secondary tuberculosis is usually caused by organisms seeded in the apices of the lungs during the primary infection. These foci may evolve soon after seeding or after a long period of dormancy. Small patches of pneumonia develop around the foci. As the disease progresses, there is an insidious onset and development of nonspecific symptoms such as fatigue, fever, anorexia, night sweats, and general wasting. Cough and sputum denote more advanced disease.

Miliary tuberculosis occurs when the tubercle bacilli gain access to the lymphatics and bloodstream and seed distant organs. Miliary lesions may develop in almost any organ of the body, but of the most favored sites are bones and joints, the genitourinary tract, meninges, lymph nodes, and peritoneum. Miliary tuberculosis in its primary infection stage, when associated with meningitis, is responsible for deaths in young children.

See Appendix 28 for more information.

Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
×

DISEASE BURDEN

Epidemiology

For the purposes of the calculations in this report, the committee estimated that there are approximately 23,000 new cases of mycobacterium tuberculosis (TB) in the United States each year. It was assumed that incidence of TB infection increases with age. It is assumed that half the cases occur in people belonging to a high-risk group and half occur in people in multi-drug resistant areas. It was estimated that there are approximately 1,500 deaths associated with TB annually. See Table A16–1.

Disease Scenarios

For the purposes of the calculation in this report, the committee assumed that most cases of TB infection result in pulmonary disease. Extrapulmonary disease is seen in the remaining 12% of infected people. The health utility index (HUI) was assumed to range from 1.0 for treatment of asymptomatic people (described below) to .89 for the 9-month treatment phase for pulmonary TB and .72 for 20 days of severe extrapulmonary TB (including hospitalization). See Table A16–2.

COST INCURRED BY DISEASE

Table 16–3 summarizes the health care costs incurred by TB infections. For the purposes of the calculations in this report, it was assumed that costs are incurred for both active and asymptomatic (suspected and latent) cases of TB. It is assumed that for every case of confirmed, active TB disease, treatment for 3 to 5 asymptomatic (suspected or latent) cases of TB is required until TB infection is confirmed. Asymptomatic, latent infections require additional treatment. These treatments are assumed to include two visits to a general physician, three visits to a nurse, diagnostic evaluation, and medications. Although the model assumes that all suspected cases of TB undergo the care described above, it is assumed that adherence to a 6-month treatment regime for latent infections is not complete (e.g., that 40% of patients take medications for only 3 months).

Health care costs incurred for pulmonary and extrapulmonary TB are assumed to involve hospitalization followed by 9 months of outpatient treatment. This follow-up involves monthly costs for a physician visit, diagnostic evaluation, and medication.

Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
×

Table A16–1 Incidence and Mortality Rates of TB Infections

Age Groups

Population

Incidence Rates (per 100,000)

% Distribution of Cases

Cases

<1

3,963,000

2.66

0.0046

106

1–4

16,219,000

2.66

0.0189

432

5–14

38,056,000

2.66

0.0445

1,014

15–24

36,263,000

4.69

0.0746

1,700

25–34

41,670,000

9.82

0.1794

4,090

35–44

42,149,000

9.82

0.1815

4,137

45–54

30,224,000

11.63

0.1542

3,515

55–64

21,241,000

11.63

0.1084

2,470

65–74

18,964,000

15.85

0.1318

3,005

75–84

11,088,000

15.85

0.0771

1,757

85+

3,598,000

15.85

0.0250

570

Total

263,435,000

8.65

1.0000

22,795

Age Groups

Population

Mortality Rates (per 100,000)

% Distribution of Cases

Cases

<1

3,963,000

0.00

0.0000

0

1–4

16,219,000

0.02

0.0020

3

5–14

38,056,000

0.00

0.0007

1

15–24

36,263,000

0.04

0.0102

15

25–34

41,670,000

0.18

0.0495

73

35–44

42,149,000

0.33

0.0928

137

45–54

30,224,000

0.50

0.1030

152

55–64

21,241,000

0.96

0.1382

204

65–74

18,964,000

1.65

0.2121

313

75–84

11,088,000

3.22

0.2419

357

85+

3,598,000

6.14

0.1497

221

Total

263,435,000

0.56

1.0000

1,476

VACCINE DEVELOPMENT

The committee assumed that it will take 15 years until licensure of a TB 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 500,000 high-risk people. 300,000 of those people are high-risk individuals in multi-drug-resistant areas. It was assumed that 90% of the selective high-risk population would utilize the vaccine and that

Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
×

Table A16–2 Disease Scenarios for TB Infection

 

No. of Cases

% of Cases

Committee HUI Values

Duration (years)

Total Deaths (from acute infection)

1,476

 

Total Cases (reported)

22,795

 

Asymptomatic—suspect

suspect cases (treatment begun)

68,385

300.00%

1.0000

0.2500 (3 months)

Asymptomatic—latent infection

preventive treatment for latent infection

113,975

500.00%

1.0000

0.5000 (6 months)

Pulmonary TB

inpatient

20,060

88.00%

0.8700

0.0548 (20 days)

Pulmonary TB

outpatient

19,057

83.60%

0.8900

0.7500 (9 months)

Extrapulmonary TB

inpatient

2,735

12.00%

0.7200

0.0548 (20 days)

Extrapulmonary TB

outpatient

2,462

10.80%

0.8600

0.7500 (9 months)

60% of the targeted population in multi-drug-resistant areas would receive the vaccine.

Vaccine Schedule, Efficacy, and Costs

For the purposes of the calculations in this report, it was estimated that this vaccine would cost $50 per dose and that administration costs would be $10 per dose. Default assumptions of a 3-dose series and 75% effectiveness were accepted. Table 4–1 summarizes vaccine program assumptions for all vaccines considered in this report.

RESULTS

If a vaccine program for TB 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 $4,000. 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 1,300.

Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
×

Table A16–3 Health Care Costs Associated with TB Infection

 

% with Care

Cost per Unit

Units per Case

Form of Treatment

Asymptomatic—suspect

 

treated (detected in screening, etc.)

 

suspect cases: 3 months treatment until culture results available

100%

$50

2.0

physician a

 

100%

$25

3.0

nurse visit

100%

$50

1.0

diagnostic a

100%

$50

3.0

medication b

Asymptomatic—latent

 

treated (detected in screening, etc.)

75%

$50

3.0

physician a

preventive treatment for latent infection: 6 months

75%

$25

6.0

nurse visit

estimated 60% complete treatment; rest complete half of treatment

100%

$50

1.0

diagnostic a

 

60%

$50

6.0

medication b: completes course

40%

$50

3.0

medication b: completes half course

Pulmonary TB

 

inpatient

100%

$6,000

1.0

hospitalization

 

100%

$100

3.0

physician b

100%

$50

1.0

diagnostic a

25%

$500

1.0

diagnostic c

Pulmonary TB

 

outpatient

100%

$50

9.0

physician a

 

100%

$50

9.0

diagnostic a

100%

$50

9.0

medication b

Extrapulmonary TB

 

inpatient

100%

$6,000

1.0

hospitalization

 

100%

$100

3.0

physician b

100%

$50

1.0

diagnostic b

25%

$500

1.0

diagnostic c

Extrapulmonary TB

 

outpatient

100%

$50

9.0

physician a

 

100%

$50

9.0

diagnostic a

100%

$50

9.0

medication b

If a vaccine program for TB 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 $100 million. Using committee assumptions of less-than-ideal efficacy and utilization and including time

Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
×

and monetary costs until a vaccine program is implemented, the annualized present value of the health care costs saved would be $34.2 million.

If a vaccine program for TB 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 $90 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 $35.9 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 a TB 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 −$3,000. 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 $9,500.

See Chapters 4 and 5 for details on the methods and assumptions used by the committee for the results reported.

READING LIST

Brewer TF, Heymann SJ, Colditz GA, et al. Evaluation of Tuberculosis Control Policies Using Computer Simulation. JAMA 1996; 276:1898–1903.

Brown RE, Miller B, Taylor WR, et al. Health-Care Expenditure for Tuberculosis in the United States. Archives of Internal Medicine 1995; 155:1595–1600.


CDC. The Role of BCG Vaccine in the Prevention and Control of Tuberculosis in the United States. Morbidity and Mortality Weekly Report 1996; 45:1–18.

CDC. Tuberculosis Morbidity—United States, 1995. Morbidity and Mortality Weekly Report 1996; 45:365–370.


Haas DW, Des Prez RM. Mycobacterium Tuberculosis. In: Principles and Practice of Infectious Diseases. GL Mandell, JE Bennett, Dolin R eds. New York, NY: Churchill Livingstone, 1995, pp. 2213–2243.


Miller B, Castro KG. Sharpen Available Tools for Tuberculosis Control, but New Tools Needed for Elimination. JAMA 1996; 276:1916–1917.


Singh GK, Kochanek KD, MacDorman MF. Advance Report of Final Mortality Statistics, 1994. Monthly Vital Statistics Report 1996; 45.

Smith MHD, Starke JR, Marquis JR. Tuberculosis and Opportunistic Mycobacterial Infections. In: Textbook of Pediatric Infectious Diseases. RD Feigin and JD Cherry eds. Philadelphia, PA: WB Saunder Company, 1992, pp. 1321–1362.

Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
×
Page 251
Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
×
Page 252
Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
×
Page 253
Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
×
Page 254
Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
×
Page 255
Suggested Citation:"Appendix 16: Mycobacterium tuberculosis." Institute of Medicine. 2000. Vaccines for the 21st Century: A Tool for Decisionmaking. Washington, DC: The National Academies Press. doi: 10.17226/5501.
×
Page 256
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Vaccines have made it possible to eradicate the scourge of smallpox, promise the same for polio, and have profoundly reduced the threat posed by other diseases such as whooping cough, measles, and meningitis.

What is next? There are many pathogens, autoimmune diseases, and cancers that may be promising targets for vaccine research and development.

This volume provides an analytic framework and quantitative model for evaluating disease conditions that can be applied by those setting priorities for vaccine development over the coming decades. The committee describes an approach for comparing potential new vaccines based on their impact on morbidity and mortality and on the costs of both health care and vaccine development. The book examines:

  • Lessons to be learned from the polio experience.
  • Scientific advances that set the stage for new vaccines.
  • Factors that affect how vaccines are used in the population.
  • Value judgments and ethical questions raised by comparison of health needs and benefits.

The committee provides a way to compare different forms of illness and set vaccine priorities without assigning a monetary value to lives. Their recommendations will be important to anyone involved in science policy and public health planning: policymakers, regulators, health care providers, vaccine manufacturers, and researchers.

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