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APPENDIX 2
Chlamydia

DISEASE BURDEN

Epidemiology

For the purposes of the calculations in this report, the committee has estimated that there are 4 million new cases of chlamydia infections in noninfants in the United States each year. These cases are split equally between men and women. The committee estimated that there are 130,000 cases annually of chlamydia infections in infants. There is very minimal mortality associated with this infection; the committee has indicated a nominal number of 5 deaths in women annually for purposes of modeling. The morbidity is extensive and manifests in many different ways.

The committee estimated that the age distribution of new chlamydia infections is the same for men and women. The vast majority (90%) of new cases in noninfants occur in people between the ages of 15 and 34 years of age. Table A2–1 illustrates the age distribution of new annual chlamydia infections in women and men used in the model.

Disease Scenarios: Women

The committee estimated that 70% of infections in women are asymptomatic and that 55% of those go untreated. 15% of asymptomatic cases are detected through screening. 30% of new infections in women are symptomatic.

See Appendix 28 for more information.



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Vaccines for the 21st Century: A Tool for Decisionmaking APPENDIX 2 Chlamydia DISEASE BURDEN Epidemiology For the purposes of the calculations in this report, the committee has estimated that there are 4 million new cases of chlamydia infections in noninfants in the United States each year. These cases are split equally between men and women. The committee estimated that there are 130,000 cases annually of chlamydia infections in infants. There is very minimal mortality associated with this infection; the committee has indicated a nominal number of 5 deaths in women annually for purposes of modeling. The morbidity is extensive and manifests in many different ways. The committee estimated that the age distribution of new chlamydia infections is the same for men and women. The vast majority (90%) of new cases in noninfants occur in people between the ages of 15 and 34 years of age. Table A2–1 illustrates the age distribution of new annual chlamydia infections in women and men used in the model. Disease Scenarios: Women The committee estimated that 70% of infections in women are asymptomatic and that 55% of those go untreated. 15% of asymptomatic cases are detected through screening. 30% of new infections in women are symptomatic. See Appendix 28 for more information.

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Vaccines for the 21st Century: A Tool for Decisionmaking TABLE A2–1 Incidence of Chlamydia in Men and Women Age Groups Male Population Incidence Rates (per 100,000) Cases <1 2,030,000 0.00 0 1–4 8,314,000 120.28 10,000 5–14 19,502,000 461.49 90,000 15–24 18,516,000 6,480.88 1,200,000 25–34 20,835,000 2,879.77 600,000 35–44 20,911,000 334.75 70,000 45–54 14,777,000 135.35 20,000 55–64 10,101,000 99.00 10,000 65–74 8,420,000 0.00 0 75–84 4,274,000 0.00 0 ≥85 1,005,000 0.00 0 Total 128,685,000 1,554.18 2,000,000 Age Groups Female Population Incidence Rates (per 100,000) Cases <1 1,933,000 0.00 0 1–4 7,905,000 126.50 10,000 5–14 18,554,000 485.07 90,000 15–24 17,747,000 6,761.71 1,200,000 25–34 20,835,000 2,879.77 600,000 35–44 21,238,000 329.60 70,000 45–54 15,447,000 129.47 20,000 55–64 11,140,000 89.77 10,000 65–74 10,544,000 0.00 0 75–84 6,814,000 0.00 0 85+ 2,593,000 0.00 0 Total 134,750,000 1,484.23 2,000,000 Health consequences of chlamydia infection in women accounted for in the model include acute urethral syndrome, mild cervicitis, pelvic inflammatory disease (PID) and its sequelae (ectopic pregnancy, chronic pelvic pain, and infertility, assumed for calculation purposes to incur costs and decreased health states with a 5-year lag from infection), Reiter’s syndrome, and arthritis. Table A2–2 illustrates the estimated number of cases in each state, the duration of time that state is experienced, and the health utility index (HUI) associated with each state. These vary greatly. At one end of the spectrum are a large number of relatively minor conditions such as acute urethral syndrome (100,000 cases experiencing three days of an HUI of .75). At the other end are many fewer

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Vaccines for the 21st Century: A Tool for Decisionmaking Table A2–2 Morbidity Scenarios for Chlamydia Infection in Women, Men and Infants   No. of Cases % of Cases Committee HUI Values Duration WOMEN Asymptomatic 1,400,000 70.0% 1.00   untreated   55.0%   treated (detected in screening, etc)   15.0%   Acute Urethral Syndrome 100,000 5.0% 0.75 0.0082 (3 days) Mild (cervicitis, bartholinitis) 500,000 25.0% 0.90 0.0767 (4 weeks) PID 280,500 14.0%   outpatient treatment only   0.63 0.0274 (10 days) PID 33,000 1.7%   inpatient treatment—no surgery   0.57 0.0055 (2 days) PID 16,500 0.8%   inpatient treatment with surgery   0.46 0.0055 2 days) PID 49,500 2.5%   outpatient treatment after inpatient treatment   0.83 0.0274 (10 days) Ectopic Pregnancy—Outpatient Treatment 14,850 0.7%   PID sequelae: 5-year lag   0.58 0.0767 (4 weeks) Ectopic Pregnancy—Inpatient Treatment 14,850 0.7%   PID sequelae: 5-year lag inpatient   0.23 0.0082 (3 days) outpatient treatment after inpatient treatment   0.66 0.0767 (4 weeks) Chronic pelvic pain 59,400 3.0%   PID sequelae: 5-year lag   0.60 22.7313 (duration remaining lifetime) Infertility 66,000 3.3%   PID sequelae: 5-year lag   0.82 22.7313 (duration remaining lifetime) Reiter’s Syndrome 2,000 0.1% 0.63 0.0384 (2 weeks) Arthritis 10,000 0.5% 0.69 0.1151 (6 weeks) MEN Asymptomatic 500,000 25.0%   untreated   1.00 0 Urethritis 1,500,000 75.0% 0.84 0.0192 (7 days) Epididymitis 36,000 1.8%   outpatient   0.46 0.0192 (7 days) Epididymitis 3,600 0.2%   inpatient   0.30 0.0082 (3 days) Reiter’s Syndrome 2,000 0.1% 0.63 0.0384 (2 weeks)

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Vaccines for the 21st Century: A Tool for Decisionmaking   No. of Cases % of Cases Committee HUI Values Duration (years) Arthritis 10,000 0.5% 0.69 0.1151 (6 weeks) INFANTS Conjunctivitis 100,000 76.9%   neonatal infection   0.97 0.5000 (6 months) Pneumonia 40,000 30.8%   outpatient   0.79 0.1667 (onset: 6 weeks; duration: 2 months) Pneumonia w/sequelae 10,000 7.7%   inpatient   0.55 0.0137 (onset: 6 weeks; duration: 5 days) cases with a much more serious decrement in health status for longer periods of time. Examples include ectopic pregnancy (14,850 cases treated as an inpatient for 3 days and 4 weeks recuperation as an outpatient at an HUI of .66) and chronic pelvic pain (59,400 cases of an HUI state of .60 for the duration of lifetime). Disease Scenarios: Men The committee estimated that 25% of infections in men are asymptomatic. The symptomatic cases all involve urethritis. A small percentage of these symptomatic infections also involve more serious manifestations, such as epididymitis, Reiter’s syndrome, and arthritis. Table A2–2 illustrates the estimated number of cases in each state, the duration of time that state is experienced, and the health utility index (HUI) associated with each state in men. These vary greatly. At one end of the spectrum are a large number of cases of urethritis (1,500,000 cases lasting 7 days with an HUI of .84). At the other end are many fewer cases with a more serious decrement in health status for longer periods of time, such as epidymitis and arthritis. Disease Scenarios: Infants The committee estimated that there are 130,00 new infections in infants each year. Most of these are neonatal conjunctivitis, but there are some cases of pneumonia. Table A2–2 illustrates the estimated number of cases in each state, the duration of time that state is experienced, and the health utility index (HUI) associated with each state in infants.

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Vaccines for the 21st Century: A Tool for Decisionmaking COSTS INCURRED BY DISEASE Table A2–3 summarizes the health care costs incurred by chlamydia infections. For the purposes of the calculations used in the report, it was assumed that women with asymptomatic infections (e.g. identified through screening) and with mild manifestations (acute urethral syndrome, cervicitis, bartholinitis) treated as an outpatient incur costs associated with a limited physician visit, an inexpensive diagnostic, and an inexpensive prescription medication. Women with pelvic inflammatory disease (PID) treated as an outpatient only incur costs associated with a limited physician visit, a specialist physician visit, a mid-level diagnostic, and an inexpensive prescription medication. More severe cases of PID requiring hospitalization are associated with hospitalization costs, specialist in-patient physician visits, and a mid-level diagnostic. Those requiring surgery incurs additional costs (e.g., surgeons, anesthesiologists, anesthetists). Outpatient costs following hospitalization include a specialist visit. Ectopic pregnancy was assumed to be associated with both outpatient and inpatient costs. The outpatient costs include a specialist visit for diagnosis for all women and, for half the women with ectopic pregnancy, lab tests and multiple follow-up visits. Inpatient costs include the hospitalization charges, physician costs, mid-level diagnostics, and costs for surgeons and anesthesiologists. Follow-up visits are also included. Chronic pelvic pain was assumed to be associated with multiple general physician visits (general and specialist), analgesics, and intermediate diagnostics. It was assumed that 75% of women with chronic pelvic pain would receive outpatient laparoscopy and associated physician charges and that 30% would require inpatient surgery with associated charges. For the purposes of the calculation, it was assumed that half of women infertile due to chlamydia infection receive treatment for infertility. Costs incurred were assumed to include multiple specialist visits and expensive diagnostics. Slightly fewer would receive outpatient laparoscopy and other surgeries. It was assumed that a small fraction would undergo in vitro fertilization. Costs incurred due to both Reiter’s syndrome and arthritis for both men and women were assumed to include two visits to a specialist and inexpensive prescription medications. Costs incurred for urethritis in men infected with chlamydia were assumed to include a limited physician visit, an inexpensive diagnostic, and an inexpensive prescription medication. Outpatient costs incurred by men with epididymitis include a limited and a specialist physician visit, and an inexpensive diagnostic and prescription medication. Inpatient costs associated with those few patients hospitalized for epididymitis include hospital costs, comprehensive in patient physician visits, medications, and surgeons and anesthesiologists for a minority who require surgery.

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Vaccines for the 21st Century: A Tool for Decisionmaking Table A2–3 Treatment Scenarios for Chlamayida Infection in Women, Men and Infants   % with Care Cost per Unit Units per Case Form of Treatment WOMEN Asymptomatic 100% $50 1 physician a 100% $50 1 diagnostic a 100% $50 1 prescription b Acute Urethral Syndrome: outpatient 100% $50 1 physician a 100% $50 1 diagnostic a 100% $50 1 prescription b Mild conditions (cervicitis, bartholinitis): outpatient 100% $50 1 physician a 100% $50 1 diagnostic a 100% $50 1 prescription b PID: outpatient only 100% $50 1 physician a 100% $100 1 physician b 100% $100 1 diagnostic b 100% $50 1 prescription b PID: inpatient—no surgery 100% $4,000 1 hospitalization 100% $150 3 physician c 100% $100 1 diagnostic b PID: inpatient with surgery 100% $4,000 1 hospitalization 100% $150 3 physician c 100% $500 4 surgical staff PID: outpatient after inpatient 100% $100 1 physician b Ectopic Pregnancy: outpatient 100% $100 1 physician b 50% $50 1 physician a 50% $100 6 follow-up physician b 10% $50 1 diagnostic a 10% $130 1 follow-up visits and tests (2 visits) outpatient laparoscopy 50% $1,250 1 laparoscopy 50% $300 2 surgeon 50% $500 2 anesthesiologist 50% $100 1 diagnostics b 50% $100 1 physician b Ectopic Pregnancy—Inpatient   PID sequelae: 5-year lag inpatient 100% $3,000 1 hospitalization 100% $150 1 physician c 100% $100 1 diagnostics b 100% $500 1 surgeon 100% $500 1 anesthesiology outpatient after inpatient 100% $100 2 physician b

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Vaccines for the 21st Century: A Tool for Decisionmaking   % with Care Cost per Unit Units per Case Form of Treatment Chronic pelvic pain   PID sequelae: 5 year lag   treatment assumed to occur 5 years after onset of infection 100% $100 1 physician b   100% $50 4 physician a 100% $100 1 analgesics (6 months) 100% $100 1 diagnostic b outpatient laparascopy 75% $1,000 1 hospital charges 75% $500 2 surgeon/anesthesiologist 75% $150 1 physician c lower abdominal surgery 30% $4,000 1 hospitalization 30% $500 1 surgeon 30% $500 1 anesthesiologist 30% $150 1 physician c 30% $50 1 post-discharge visit (physician a) Infertility   PID sequelae: 5-year lag 50% $150 6 physician c treatment assumed to occur 5 years after onset of infection 50% $500 1 diagnostic c   38% $1,000 1 outpatient laparoscopy hospitalization 38% $500 2 surgeon/anesthesiologist 38% $150 1 physician c tubal surgery 15% $1,000 1 outpatient surgery 15% $500 2 surgeon/anesthesiologist 15% $150 1 physician c Reiter’s Syndrome 100% $100 2.0 physician b 100% $50 1.0 medication b Arthritis 100% $100 2.0 physician b 100% $50 1.0 medication b MEN Urethritis 100% $50 1 physician a 100% $50 1 diagnostics a 100% $50.00 1 medication b Epididymitis: outpatient 100% $100 1 physician b 100% $50 1 physician a 100% $50 1 diagnostics a 100% $50 1 medication b

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Vaccines for the 21st Century: A Tool for Decisionmaking   % with Care Cost per Unit Units per Case Form of Treatment Epididymitis: inpatient 100% $3,000 1 hospitalization 100% $150 3 physician c 100% $50 1 medication b 0.03 $500 2 surgical staff Reiter’s Syndrome 100% $100 2.0 physician b 100% $50 1.0 medication b Arthritis 100% $100 2.0 physician b 100% $50 1.0 medication b INFANTS Conjunctivitis: neonatal infection 100% $50 1 limited visit   100% $50 1 diagnostics a 100% $50 1 medication b Pneumonia: outpatient 100% $100 2 physician b 100% $100 1 diagnostic b 100% *$50 1 medication b Pneumonia w/sequelae: inpatient 100% $4,000 1 hospital (3 days)   100% $150 1 comprehensive 100% $100 1 intermediate 100% $50 2 brief 100% $50 1 diagnostic 100% $50 1 medication b and prescription medications. Inpatient costs for the smaller number of infants with pneumonia requiring hospitalization include hospitalization costs, physician visits (specialists and general), diagnostics, and medications. VACCINE DEVELOPMENT The committee assumed that the development of a chlamydia vaccine is feasible and that licensure can occur within the time frame of its charge, but is not imminent. The estimates for the model are that it will take 15 years until licensure and that $360 million needs to be invested. 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 committee’s model assumes that chlamydia immunization will occur during puberty. As described in the body of the report, for these purposes, that is set at 12 years of age. Both males and females would receive the immunization. It is estimated that only 50% of the target population will accept the immunization. Vaccine Schedule, Efficacy, and Costs The committee estimated that this would be a relatively low-cost vaccine, costing $50 per dose. 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 Chlamydia 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 525,000. 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 110,000. Although the number of new chlamydia infections in men equal those in women in this model, the number of QALYs lost due to disease in men is much less due to the decreased severity of the disease experienced in men. If a vaccine program for Chlamydia 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 $850 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 $175 million. If a vaccine program for Chlamydia 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 $680 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 $190 million.

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Vaccines for the 21st Century: A Tool for Decisionmaking Using committee assumptions of time and costs until licensure, the fixed cost of vaccine development has been amortized and is $11 million for a Chlamydia 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 -$350. 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 $200. See Chapters 4 and 5 for details on the methods and assumptions used by the committee for the results reported. READING LIST Alexander LL, Treiman K, Clarke P. A National Survey of Nurse Practitioner Chlamydia Knowledge and Treatment Practices of Female Patients. Nurse Practitioner 1996; 21:48, 51–4. CDC. Ectopic Pregnancy—United States, 1990–1992. Morbidity and Mortality Weekly Report 1995; 44:46–48. CDC. Evaluation of Surveillance for Chlamydia trachomatis Infections in the United States, 1987 to 1991. Morbidity and Mortality Weekly Report 1993; 42:21–27. CDC. Recommendations for the Prevention and Management of Chlamydia trachomatis Infections. Morbidity and Mortality Weekly Report 1993; 42:1–4. Institute of Medicine. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Eng TR, Butler WT (eds.). Washington, DC: National Academy Press, 1997. Jones RB. Chlamydia trachomatis (trachoma perinatal infections, lymphogranuloma vernereum, and other genital infections). In: Principles and Practice of Infectious Diseases. GL Mandell,, JE Bennett, Dolin R eds. New York, NY: Churchill Livingstone, 1995, pp. 1679–1693. Magid D, Douglas JM, Schwartz JS. Doxycycline Compared with Azithromycin for Treating Women with Genital Chlamydia trachomatis Infections: An Incremental Cost-Effectiveness Analysis. Annals of Internal Medicine 1996; 124:389–99. 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.