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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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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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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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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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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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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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% 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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% 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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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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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.
Representative terms from entire chapter:
committee estimated
