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APPENDIX 25
Streptococcus, Group B

DISEASE BURDEN

Epidemiology

For the purposes of the calculations in this report, the committee estimated that there are approximately 7,000 new infections with streptococcus, group B (GBS) and 430 deaths in infants and 4,000 new GBS infections (and no deaths) in pregnant women each year. It is also assumed that there are approximately 11,000 new GBS infections and 2,300 deaths in nonpregnant adults. The highest incidence of disease in nonpregnant adults is in people 65 years of age and older. See Table A25–1.

Disease Scenarios

For the purposes of the calculations in this report, the committee assumed that 90% of GBS disease in neonates is early-onset disease and 20% is late-onset disease. Disease associated with neonatal GBS infections includes bacteremia (86%) and meningitis (14%). Approximately 72% of neonatal GBS infections are early-onset bacteremia, 14% are late-onset bacteremia, 8% are early-onset meningitis, and 6% are late-onset meningitis.

For the purposes of the calculations in the report, the committee assumed that all pregnant women infected with GBS experience chorioamnionitis, endometritis, or bacteremia. These infections are assumed to be associated with 7 days at an HUI of .68. It was assumed that all nonpregnant adults infected



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Vaccines for the 21st Century: A Tool for Decisionmaking APPENDIX 25 Streptococcus, Group B DISEASE BURDEN Epidemiology For the purposes of the calculations in this report, the committee estimated that there are approximately 7,000 new infections with streptococcus, group B (GBS) and 430 deaths in infants and 4,000 new GBS infections (and no deaths) in pregnant women each year. It is also assumed that there are approximately 11,000 new GBS infections and 2,300 deaths in nonpregnant adults. The highest incidence of disease in nonpregnant adults is in people 65 years of age and older. See Table A25–1. Disease Scenarios For the purposes of the calculations in this report, the committee assumed that 90% of GBS disease in neonates is early-onset disease and 20% is late-onset disease. Disease associated with neonatal GBS infections includes bacteremia (86%) and meningitis (14%). Approximately 72% of neonatal GBS infections are early-onset bacteremia, 14% are late-onset bacteremia, 8% are early-onset meningitis, and 6% are late-onset meningitis. For the purposes of the calculations in the report, the committee assumed that all pregnant women infected with GBS experience chorioamnionitis, endometritis, or bacteremia. These infections are assumed to be associated with 7 days at an HUI of .68. It was assumed that all nonpregnant adults infected

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Vaccines for the 21st Century: A Tool for Decisionmaking Table A25–1 Incidence of Group B Streptococcus Infection in Noninfants and Nonpregnant Women Age Groups Population Incidence Rates (per 100,000) Cases <1 3,963,000 0.00 0 1–4 16,219,000 0.92 149 5–14 38,056,000 0.91 347 15–24 36,263,000 1.70 616 25–34 41,670,000 1.76 731 35–44 42,149,000 1.68 708 45–54 30,224,000 4.84 1,464 55–64 21,241,000 8.31 1,766 65–74 18,964,000 11.57 2,194 75–84 11,088,000 22.69 2,516 85+ 3,598,000 22.70 817 Total 263,435,000 4.29 11,308 with GBS experience invasive disease (e.g., bacteremia, sepsis, soft tissue infections) associated with 19 days at an HUI of .66. See Table A25–2. COST INCURRED BY DISEASE Table A25–3 summarizes the health care costs incurred by GBS infections. For the purposes of the calculations in this report, it was assumed that GBS infections in pregnant women are associated with additional hospitalization at the time of delivery and associated inpatient and outpatient physician visits and medication. Costs are also included for screening for GBS and chemoprophylaxis of pregnant women. It was estimated that all nonpregnant adults with invasive GBS disease require hospitalization (including inpatient physician visits) and outpatient services as well. For the calculation in this report, it was assumed that all infants with GBS require hospitalization, including multiple inpatient physician visits and diagnostics. It was assumed that a small percentage of infants with GBS meningitis will require long-term care for 10 years until death. VACCINE DEVELOPMENT The committee assumed that it will take 7 years until licensure of a GBS vaccine and that $300 million needs to be invested for approval for use in nonpregnant people, and an additional $100 million needs to be invested for that same vaccine to be used in pregnant women. Special considerations regarding

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Vaccines for the 21st Century: A Tool for Decisionmaking Table 25–2 Disease Scenarios for Group B Streptococcus Infection in Infants and Adults   % of Cases Committee HUI Values Duration (years) INFANTS   Bacteremia—NICU 36.0% 0.24 0.027 (10 days) Bacteremia—Non-NICU 36.0% 0.24 0.027 (10 days) Meningitis 6.4% 0.27 0.047 (17 days) Meningitis with impairment 1.1%   acute care (50% NICU; 50% Level 2)   0.27 0.047 (17 days) permanent impairment—normal lifespan   0.53 26.804 (discounted quality adjusted life expectancy at birth) Meningitis with early death 0.5%   acute care   0.27 0.047 (17 days) permanent impairment   0.53 10.000 (10 years) death by age 10   0.00 25.690 (discounted quality adjusted life expectancy at age 10) LATE ONSET DISEASE—20% of infant cases Bacteremia 14.0% 0.69 0.027 (10 days) Meningitis 4.8% 0.27 0.047 (17 days) Meningitis with impairment 0.8%   acute care   0.27 0.047 (17 days) permanent impairment—normal lifespan   0.53 26.804 (discounted quality adjusted life expectancy at birth) Meningitis with early death 0.4%   acute care   0.27 0.047 (17 days) permanent impairment   0.53 10.000 (10 years) death by age 10   0.00 25.690 (discounted quality adjusted life expectancy at age 10) ADULTS   Maternal Infection 100%   inpatient   0.68 0.0192 (7 days) outpatient treatment   0.0137 (5 days) NONPREGNANT ADULTS   Invasive disease 100.0%   soft tissue, bone infection; bacteremia; urosepsis; pneumonia   0.66 0.052 (19 days)

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Vaccines for the 21st Century: A Tool for Decisionmaking Table 25–3 Health Care Costs Associated with GBS Disease in Infants and Adults   % with Care Cost per Unit Units per Case Form of Treatment INFANTS   EARLY ONSET DISEASE—80% of infant cases Bacteremia—NICU   bacteremia, sepsis, pneumonia 100% $12,000 1.0 hospitalization NICU   100% $150 10.0 physician c 100% $500 1.0 diagnostic c Bacteremia—Level 2 care   bacteremia, sepsis, pneumonia 100% $7,000 1.0 hospitalization non-NICU   100% $150 10.0 physician c 100% $500 1.0 diagnostic c Meningitis   acute care 50% $12,000 1.0 hospitalization NICU   50% $7,000 1.0 hospitalization 100% $150 17.0 physician c 100% $500 1.0 diagnostic c Meningitis with impairment   acute care 50% $12,000 1.0 hospitalization NICU   50% $7,000 1.0 hospitalization 100% $150 17.0 physician c 100% $500 1.0 diagnostic c permanent impair-ment normal lifespan* 100% $225 365.0 long-term care*/per year Meningitis with early death   acute care 50% $12,000 1.0 hospitalization NICU   50% $7,000 1.0 hospitalization 100% $150 17.0 physician c 100% $500 1.0 diagnostic c permanent impair-ment for 10-year period** 100% $225 365.0 long-term care*/per year LATE ONSET DISEASE—20% of infant cases Bacteremia   bacteremia, sepsis, pneumonia 100% $7,000 1.0 hospitalization   100% $150 10.0 physician c 100% $500 1.0 diagnostic c Meningitis   acute care 50% $12,000 1.0 hospitalization NICU   50% $7,000 1.0 hospitalization 100% $150 17.0 physician c 100% $500 1.0 diagnostic c Meningitis with impairment   acute care 50% $1,200 1.0 hospitalization NICU   50% $7,000 1.0 hospitalization 100% $150 10.0 physician c

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Vaccines for the 21st Century: A Tool for Decisionmaking   % with Care Cost per Unit Units per Case Form of Treatment   100% $500 1.0 diagnostic c permanent impairment normal lifespan* 100% $225 365.0 long-term care*/per year Meningitis with early death   acute care 50% $12,000 1.0 hospitalization NICU   50% $7,000 1.0 hospitalization NICU 50% $150 10.0 physician c 50% $500 1.0 diagnostic c permanent impairment for 10-year period** 100% $225 365.0 long-term care*/per year PREGNANT WOMEN   Maternal Infection (chorioamnionitis, endometritis, bacteremia) additional inpatient treatment at time of delivery 100% $1,000 1.0 hospitalization (in addition to normal delivery)   100% $150 1.0 physician c 100% $50 1.0 medication b outpatient treatment 100% $100 1.0 physician b screening 90% $50 1.0 diagnostic a intrapartum chemoprophylaxis 25% $50 1.0 medication b NONPREGNANT ADULTS   Invasive disease   soft tissue, bone infection bacteremia; urosepsis; pneumonia 100% $4,000 1.0 hospitalization   100% $150 19.0 physician c 100% $500 1.0 diagnostic c outpatient 100% $100 2.0 physician b NOTE: *long-term care—$225/day is maintenance expenditure per resident for residential facilities for persons with mental retardation. **cost per case is calculated as “present value” of annual cost for remaining life time (life expectancy at birth or 10 years, depending on scenario); additional discounting for immunization interval development of a vaccine for use in pregnant women is discussed within the body of the report. Table 4–1 summarizes vaccine development assumptions for all vaccines considered in this report.

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Vaccines for the 21st Century: A Tool for Decisionmaking VACCINE PROGRAM CONSIDERATIONS Target Population The results of two vaccine strategies will be described. Both strategies involve annual immunization of 2,600,000 high-risk, nonpregnant adults (65 years of age or with specific chronic diseases). Both strategies involve immunization of younger females. One strategy involves annual immunization of pregnant women (approximately 1,630 primiparas). The other strategy involves annual immunization of 1,840,000 12-year-old girls. For the purposes of the calculations in this report, it is assumed that 30% of high-risk adults, 50% of 12-year-old girls, will utilize the vaccine. Additionally, it was assumed that utilization of the vaccine by pregnant women will either be 10% or 90%. 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 Immunization of Pregnant Women and At-Risk Adults If a vaccine program for group B 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 37,400. 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 10,200 for 90% utilization by pregnant women and 4,500 for 10% utilization by pregnant women. If a vaccine program for group B 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 $630 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 $310 million for 90% utilization by pregnant women and $45 million for 10% utilization by pregnant women. If a vaccine program for group B streptococci were implemented today and the vaccine was 100% efficacious and utilized by 100% of the target population,

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Vaccines for the 21st Century: A Tool for Decisionmaking the annualized present value of the program cost would be $760 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 $285 million for 90% utilization by pregnant women and $120 million for 10% utilization by pregnant women. 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 B 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 $3,400. 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 -$1,500 for 90% utilization by pregnant women and $20,000 for 10% utilization by pregnant women. A negative value represents a saving in costs in addition to a saving in QALYs. See Chapters 4 and 5 for details on the methods and assumptions used by the committee for the results reported. Immunization of Girls at Puberty and At-Risk Adults If a vaccine program for group B streptococci 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 33,000. 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 6,200. If a vaccine program for group B 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 $435 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 $125 million. If a vaccine program for group B 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 $800 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 $215 million. Using committee assumptions of time and costs until licensure, the fixed cost of vaccine development has been amortized and is $9 million for a group B streptococci vaccine.

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Vaccines for the 21st Century: A Tool for Decisionmaking 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 $11,000. 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 $16,000. See Chapters 4 and 5 for details on the methods and assumptions used by the committee for the results reported. READING LIST Anthony BF. Group B Streptococcal Infections. In: Textbook of Pediatric Infectious Diseases. RD Feigin and JD Cherry eds. Philadelphia, PA: WB Saunder Company, 1992, pp. 1305–1316. Blumberg HM, Stephens DS, Modansky M, et al. Invasive Group B Streptococcal Disease: The Emergence of Serotype V. Journal of Infectious Diseases 1996; 173:365–73. CDC. Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP). Morbidity and Mortality Weekly Report 1996; 45:1–24. CDC. Prevention of perinatal group B Streptococcal disease: a public health perspective. Morbidity and Mortality Weekly Report 1996; 45:1–24. Edwards MS, Baker CJ. Streptococcus Agalactiae (Group B Streptococcus). In: Principles and Practice of Infectious Diseases. GL Mandell, JE Bennett, Dolin R eds. New York, NY: Churchill Livingstone, 1995, pp. 1835–1845. Farley MM. A Population-Based Assessment of Invasive Disease Due to Group B Streptococcus in Nonpregnant Adults. The New England Journal of Medicine 1993; 328:1807–1811. Farley MM. Group B Streptococcal Infection in Older Patients. Drugs & Aging 1995; 6:293–300. Jackson LA, Hilsdon R, Farley MM, et al. Risk Factors for Group B Streptococcal Disease in Adults. Annals of Internal Medicine 1995; 123:415–420. U.S. Bureau of the Census. Statistical Abstract of the U.S.: 1995 (115th edition). Washington, DC, 1995. Ventura SJ, Martin JA, Mathews TJ, et al. Advance Report of Final Natality Statistics, 1994. Monthly Vital Statistics Report 1996; 44.