For the purposes of the calculations in this report, the committee estimated that there are 4,000,000 new cases of noninvasive Group A Streptococcus (GAS) per year in the United States. These cases were assumed to occur in people 24 years of age and under, with the highest incidence rate in children between the ages of 5 and 14 years. It was assumed that there was no mortality associated with noninvasive GAS disease. It was estimated that there, an additional 15,000 cases of invasive GAS disease and that the incidence rate of approximately 5.7 per 100,000 is the same in all age groups. It was assumed that 10% of invasive GAS disease is fatal. See Table A24–1.

For the purposes of the calculation in this report, the committee assumed that 100% of noninvasive GAS infections result in a limited morbidity lasting 4 days and associated with a health utility index (HUI) of 0.9. The committee estimated that a small percentage of these patients (2,000) develop acute rheumatic fever and experience a more prolonged (28 days) illness associated with an HUI of .54. A very small number of those patients then go on to experience a chronic morbidity associated with an HUI of .82 for the duration of their lifetime.

For the purposes of this report, the committee assumed that invasive GAS disease manifests as necrotizing fasciitis (with and without lifetime sequelae) in 10% of cases and toxic shock (lasting 15 days and associated with HUIs of .16 during hospitalization and .58 following hospitalization) for 10% of cases. 80% of the invasive forms of the disease are associated with 2 weeks of illness and HUIs of .62 and .73 for the time spent inpatient and outpatient, respectively. See Table A24–2.

Table A24–3 summarizes the health care costs incurred by GAS infections. For the purposes of the calculations in this report, it was assumed that all pa-

tients with acute, noninvasive GAS disease seek outpatient medical attention (physician, diagnostics, medication). It was also assumed that all patients experiencing acute rheumatic fever require hospitalization and associated costs. The small number of patients with chronic rheumatic disease require 2 physician visits per year for the duration of their lifetime.

For the purposes of this report, it was also assumed that all patients with fasciitis require hospitalization. The costs for severe fasciitis are approximately twice that for moderate fasciitis. Lifelong sequelae associated with necrotizing fasciitis were presumed to occur in most patients and were associated with yearly aftercare costs in approximately half of the patients.

Patients with toxic shock from GAS were presumed to require hospitalization, with 10% requiring ventilator support and more expensive care. All patients with toxic shock were presumed to also require outpatient visits to a specialist and additional medication. Other forms of invasive disease were presumed to be associated with a hospitalization and subsequent outpatient visits to a specialist and additional medication.

The committee assumed that it will take 15 years until licensure of a GAS vaccine and that $400 million needs to be invested. Table 4–1 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 target population for a GAS vaccine is all infants. It was assumed that 90% of the target population would utilize the vaccine.

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.

If a vaccine program for group A streptococci were implemented today and the vaccine were 100% efficacious and utilized by 100% of the target population, the annualized present value of the QALYs gained would be 16,500. 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 6,200.

If a vaccine program for group A streptococci 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 $495 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 $185 million.

If a vaccine program for group A streptococci 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 $720 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 $360 million.

Using committee assumptions of time and costs until licensure, the fixed cost of vaccine development has been amortized and is $12 million for a group A streptococci vaccine.

If a vaccine program were implemented today and the vaccine was 100% efficacious and utilized by 100% of the target population, the annualized present value of the cost per QALY gained is $14,000. 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 $30,000.

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

Bisno AL. Streptococcus Pyogenes. In: Principles and Practice of Infectious Diseases. GL Mandell, JE Bennett, Dolin R eds. New York, NY: Churchill Livingstone, 1995, pp. 1786–1799.

Kaplan EL. Group A Streptococcal Infections. In: Textbook of Pediatric Infectious Diseases. RD Feigin and JD Cherry eds. Philadelphia, PA: WB Saunder Company, 1992, pp. 1296–1305.