TABLE 2.
Parameters of the basic model that vary by scenario
| Name | Meaning | Standard value (range)
|
Derivation (reference[s]) | ||
|---|---|---|---|---|---|
| Baseline (no antiviral use) | Scenario 1 (current antiviral use) | Scenario 2 (increased antiviral use) | |||
| dSU | Rate at which persons with untreated, sensitive RHL episodes cease shedding | 0.17 day−1 | 0.17 day−1 | 0.17 day−1 | Calculated from duration of shedding in clinical trial controls (52) (rate = 1/duration); may be a slight overestimate as shedding may begin before symptoms |
| dST | Rate at which persons with treated, sensitive RHL episodes cease shedding | NAa | 0.4 (0.26–0.85) day−1 | 0.23 day−1 | From duration of shedding in trials of oral ACV and famciclovir (2, 52, 53) (scenario 1) and topical PCV (52) (scenario 2); presymptomatic shedding may reduce this estimate modestly, as described above |
| f | Avg rate at which individuals infected with sensitive virus experience new RHL episodes | 0.004 day−1 | 0.004 day−1 | 0.004 day−1 | Baseline calculated from the prevalence of HSV-1 seropositivity (48, 63) and the prevalence and frequency of RHL (23, 31, 47); effect of current usage would be negligible in suppressing RHL at the population level, although it would be effective for individuals (44, 51, 57), because a small proportion of the HSV-1-positive population uses antivirals currently; topical PCV (scenario 2) would not affect recurrence rate |
| p | Proportion of individuals infected with sensitive virus who treat their RHL episodes with topical PCV | 0 | 0.15–2.5% | 20% (10–30%) | Marketing projections from SmithKline Beecham, based on experience with OTC topical ACV cream in the United Kingdom (P. Johnston, personal communication) |
a
NA, not applicable.