Selected model variables
| Variable | Value (plausible range) | Reference |
|---|---|---|
| HSV-2 = herpes simplex virus type 2. ELISA = enzyme linked immunosorbent assay. When only a single estimate was available for a model parameter, we used upper and lower confidence intervals if available, or varied parameter estimates by ± 20%. | ||
| *In individuals who experienced a primary genital herpes syndrome, the first symptomatic episode of genital herpes was assigned an average duration of 9–12 days. In the absence of primary genital herpes, the first symptomatic episode was assumed to have an average duration of 4 days, equivalent to the duration of recurrent episodes of genital herpes. The probability of hospitalisation was considered to be 2% in men, and 8% in women, based on the probability of severe aseptic meningitis or autonomic dysfunction requiring urinary catheterisation.1,54 | ||
| †Based on population distribution of frequency of symptomatic relapses in the first year of infection, combined with an average duration of relapse of 4 days,19,55–57 and a linear decline in symptom frequency of 0.7 relapses/year.2,8,35 Assumes that individuals with greater than 6 relapses/year are treated with suppressive acyclovir, resulting in a 90% reduction in relapse frequency.68,69 | ||
| ‡Upper bound estimates for the future incidence and costs of neonatal HSV-2 infection were obtained by introducing a 1/10 000 risk of maternal-fetal transmission of HSV-2 for pregnant women with chronic HSV-2 infection. | ||
| §All costs were discounted to present value using a 3% real discount rate,64 and were converted to 1999 $US using the US Consumer Price Index for medical goods and services.43 The full costs of tests and vaccine administration also include medical services and patient time costs associated with clinic visits. Average hourly wage was estimated to be $14.43 Individuals screened prior to vaccine administration were assumed to require a total of four clinic visits (one for screening, and three for vaccine administration), while those vaccinated without screening required only three clinic visits. | ||
| || The cost of western blot was estimated to be approximately two thirds the charge for this test in a reference laboratory.65 | ||
| ¶The cost of ELISA was based on the list prices of test kits (provided by representatives of Diagnology Inc, Research Triangle Park, NC, USA; Meridian Diagnostics, Cincinnati, OH, USA; and MRL Diagnostics, Cypress, CA, USA) combined with 3 hours of technician time required for performance and interpretation of the test. Upper bound cost estimates were based on the list price of a test that can be performed by providers at point of care.59 | ||
| **Calculated as a weighted average of costs of primary HSV-2 without hospitalisation (two clinic visits, 7 day course of aciclovir, and 2 days off work), and with hospitalisation (costs of hospitalisation and medications with HSV-2 as a primary diagnosis and cost of 1 week off work). | ||
| ††Based on Georgia Medicaid reimbursement of physician and test costs, and lost wages due to 2 hour patient time costs.5 | ||
| Initial prevalence of HSV-2 infection (%) | National Health and Nutrition Examination Survey3 | |
| Men | 13 (6–24) | |
| Women | 23 (6–43) | |
| Annual probability of infection by infected partner (%) | 3, 13, 14, 20, 51 | |
| Men | 5 (3–11) | |
| Women | 18 (5–22) | |
| Probability of symptomatic disease among infected individuals (%) | 40 (9–50) | 3, 20, 22 |
| Probability of primary HSV-2 syndrome (%)* | 50 (35–80) | 1, 52–54 |
| Average future symptom days among individuals with symptomatic infection† | 7, 8, 19, 55–57 | |
| Men | 87 | |
| Women | 66 | |
| Relative risk of transmission with regular condom use | 0.50 (0.10–0.75) | 12–16 |
| Test characteristics | ||
| Western blot | 28, 30, 58 | |
| Sensitivity (%) | 100 | |
| Specificity (%) | 100 | |
| Type specific ELISA | 30, 59, 60 | |
| Sensitivity (%) | 96 (80–100) | |
| Specificity (%) | 97 (80–100) | |
| Average live births rate per 1000 women (1980–97) | ||
| 15–19 year old women | 53 | 36 |
| 20–29 year old women | 114 | |
| 30–39 year old women | 43 | |
| Probability (%) of HSV-2 infected infant‡ | ||
| Mother infected in third trimester | 10 (5–25) | 9, 10 |
| Mother chronically infected | 0 (0–0.5) | 9, 10, 61, 62 |
| Probability (%) of death in HSV-2 infected infant | 14 (8–21) | 25–27, 42, 63 |
| Probability (%) of long term sequelae in HSV-2 infected infant | 40 (30–50) | 25–27, 42, 63 |
| Discount rate (%) | 3 (0–10) | 64 |
| Costs§ | ||
| Western blot || | $60 ($45–$90) | 65 |
| ELISA | $5 ($3–$35) | ¶ |
| Condoms (per month) | $3 ($1–$10) | 13, 24, 37–39 |
| Treatment for primary genital herpes syndrome** | ||
| Men | $450 ($360–$540) | 1, 5, 6, 41, 54, 66 |
| Women | $800 ($640–$960) | |
| Aciclovir | ||
| Relapse | $16 ($9–$35) | 40, 41 |
| Suppressive therapy (monthly cost) | $40 ($20–$215) | |
| Clinic visit related to genital herpes†† | $120 ($90–$145) | 5, 43 |
| Excess obstetrical costs associated with history of symptomatic HSV-2 infection | $300 ($130–$770) | 5, 63 |
| Lifetime costs of neonatal HSV-2 infection | $110 000 ($85 000–$860 000) | 5, 25–27, 42, 63, 67 |