Targeted antiviral prophylaxis
The impact of changing the necessary tracing period and the actual coverage of tracing persons in contact with a patient for the TAP intervention were investigated (Fig. 4). The mean numbers of total patients and persons treated with antiviral drugs for prophylaxis with 95% confidence intervals (CIs) for 90 days after the introduction of the initial patient and also the numbers of cases prevented per person treated with antiviral drugs for prophylaxis are shown in Table 4. For situations with a necessary tracing period of 6 days with 30% coverage and 2 days with 70%, the mean number of total patients for 90 days would be decreased to 4.0 and 1.2%, respectively, compared with the baseline. The ripple effect of the administration of antiviral drugs in TAP on the reduction in patient numbers was estimated to be 27.6- and 37.5-fold, respectively, for these situations, indicating that the TAP intervention would have a substantial effect in suppressing the spread of the infection.
Fig. 4 Comparison of the total number of patients (a) and the number treated with antiviral drugs (b) for 90 days with a tracing coverage of 30, 50, and 70%, respectively, and a necessary tracing period of 2, 4, and 6 days, respectively, for the targeted antiviral prophylaxis (TAP) intervention. The squares show the mean value for 100-trial simulations with error bars showing the 95% confidence interval (CI). Grey, light grey, and white squares show the situations for necessary tracing periods of 2, 4, and 6 days, respectively
Table 4 Summary of results for TAP and STAP
Intervention Coverage (%) Necessary tracing period Total number of patients Number of treated persons Number of cases prevented/no. of treated persons
(days) Mean (95% CI) Mean (95% CI)
TAP 30 2 5,244 (3,738, 6,750) 5,018 (4,081, 5,955) 38.1
4 7,299 (5,398, 9,201) 6,612 (5,643, 7,581) 28.6
6 7,790 (5,600, 9,980) 6,824 (5,716, 7,931) 27.6
50 2 3,093 (2,039, 4,147) 4,923 (3,897, 5,949) 39.2
4 4,643 (3,446, 5,841) 7,258 (6,052, 8,464) 26.4
6 7,274 (5,234, 9,314) 10,050 (8,238, 11,861) 18.8
70 2 2,299 (1,586, 3,013) 5,167 (4,091, 6,242) 37.5
4 3,618 (2,529, 4,707) 7,206 (5,704, 8,708) 26.7
6 6,492 (4,376, 8,608) 10,637 (8,511, 12,763) 17.8
STAP 30 2 2,681 (2,215, 3,148) 17,094 (15,083, 19,106) 11.3
4 2,723 (2,238, 3,209) 19,339 (16,717, 21,960) 10.0
6 2,984 (2,575, 3,392) 18,925 (16,687, 21,162) 10.2
50 2 2,473 (2,103, 2,844) 25,494 (22,067, 28,921) 7.6
4 2,758 (2,361, 3,156) 24,451 (21,502, 27,400) 7.9
6 2,893 (2,462, 3,324) 22,971 (20,319, 25,623) 8.4
70 2 2,496 (2,117, 2,874) 31,638 (27,647, 35,628) 6.1
4 2,538 (2,079, 2,996) 31,260 (27,163, 35,357) 6.2
6 2,698 (2,245, 3,151) 27,938 (24,276, 31,601) 6.9
CI Confidence interval