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APPENDIX 5
Enterotoxigenic E. coli

DISEASE BURDEN

Epidemiology

Enterotoxigenic E. coli (ETEC) is a common causes of “traveler’s diarrhea” and a very important cause of diarrhea in infants in developing countries. ETEC can produce nausea, abdominal cramps, low fever, and a sudden-onset profuse watery diarrhea that is like a mild cause of cholera. Traveler’s diarrhea can be severe but is rarely fatal. For the purposes of the calculations in this report, the committee estimated that there are 660,000 new cases of ETEC infection each year in the United States. The incidence rate is 250 per 100,000 within all age groups and in both males and females. It is assumed that 90% of the infections occur in travelers. There are no deaths associated with ETEC infection for the purposes of the modeling in this report.

Disease Scenarios

For the purposes of the calculation in this report, the committee assumed that the vast majority of infections manifest as mild to moderate diarrhea lasting 4 days and associated with a health utility index (HUI) of .75. For 10% of the patients, the diarrhea was estimated to last 8 days.



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Vaccines for the 21st Century: A Tool for Decisionmaking APPENDIX 5 Enterotoxigenic E. coli DISEASE BURDEN Epidemiology Enterotoxigenic E. coli (ETEC) is a common causes of “traveler’s diarrhea” and a very important cause of diarrhea in infants in developing countries. ETEC can produce nausea, abdominal cramps, low fever, and a sudden-onset profuse watery diarrhea that is like a mild cause of cholera. Traveler’s diarrhea can be severe but is rarely fatal. For the purposes of the calculations in this report, the committee estimated that there are 660,000 new cases of ETEC infection each year in the United States. The incidence rate is 250 per 100,000 within all age groups and in both males and females. It is assumed that 90% of the infections occur in travelers. There are no deaths associated with ETEC infection for the purposes of the modeling in this report. Disease Scenarios For the purposes of the calculation in this report, the committee assumed that the vast majority of infections manifest as mild to moderate diarrhea lasting 4 days and associated with a health utility index (HUI) of .75. For 10% of the patients, the diarrhea was estimated to last 8 days.

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Vaccines for the 21st Century: A Tool for Decisionmaking COST INCURRED BY DISEASE Table A5–1 summarizes the health care costs incurred by ETEC infections. For the purposes of the calculations in this report, it was assumed that all people infected with ETEC use over-the-counter medications and that only a small fraction see a physician. Costs for additional diapers and oral rehydration are included for some of the infected individuals, whether travelers or not. It is these costs which are increased for those who experience a more prolonged diarrhea. VACCINE DEVELOPMENT The estimates for the model are that it will take 7 years until licensure and that $240 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 target population was estimated to include the annual birth cohort and overseas travelers. For the purposes of this report, the number of targeted travelers is 2,500,000 annually. It is estimated that 90% of infants and 30% of travlers will receive the immunization. Vaccine Schedule, Efficacy, and Costs The committee estimated that this vaccine would cost $50 per dose and that 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 ETEC 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 1,600. 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 280.

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Vaccines for the 21st Century: A Tool for Decisionmaking Table A5–1 Health Care Costs Associated with ETEC Disease   % of Cases Duration (years) % with Care Cost per Case Cost per Unit Units per Case Form of Treatment Mile-moderate illness 90%   Diarrhea   0.0110 100% $10 $10 1.0 Medication A 0.0110 15% $50 $50 1.0 Physician A 0.0110 15% $10 $10 1.0 Other costs (diapers/oral rehydration therapy) Prolonged illness 10%   Acute manifestations   0.0219 100% $10 $10 1.0 Medication A 0.0219 15% $50 $50 1.0 Physician A 0.0219 15% $20 $10 2.0 Other costs (diapers/oral rehydration therapy)

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Vaccines for the 21st Century: A Tool for Decisionmaking If a vaccine program for ETEC 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 $11.7 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 $2 million. If a vaccine program for ETEC 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 $1.2 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 program cost would be $550 million. Using committee assumptions of time and costs until licensure, the fixed cost of vaccine development has been amortized and is $7.2 million for a ETEC 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 $700,000. 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 $2 million. See Chapters 4 and 5 for details on the methods and assumptions used by the committee for the results reported. READING LIST Braden C, Keusch GT. Diarrhea and Dysentery-Causing Escherichia Coli. In: Textbook of Pediatric Infectious Diseases. RD Feigin and JD Cherry eds. Philadelphia, PA: WB Saunder Company, 1992, pp. 607–620.