| |
|
|
Table 1. Sensitivity analyses: Effect on number of cases of smallpox as a result of variations in numbers initially infected, numbers infected per infectious
person, intervention start days, and quarantine and vaccination effectiveness. |
|
| No. initially
infecteda |
No. infected per
infectious personb |
Start dayc |
Quarantine: %
removal per dayd |
Vaccination: %
reduction in
transmissione |
Cumulative total
cases at 365 days |
Daily cases at 365
days |
Increase or
decrease
(+/–f ) |
|
| 100 |
2 |
30 |
10 |
Nilg |
1.5 million |
32,548 |
+ |
| 100 |
2 |
30 |
25 |
Nil |
2,455 |
2 |
– |
| 100 |
2 |
30 |
10 |
25 |
10,512 |
51 |
+ |
| 100 |
2 |
45 |
10 |
33 |
6,063 |
8 |
– |
| 100 |
2 |
45 |
25 |
33 |
1,548 |
0 |
– |
| 100 |
2 |
45 |
25 |
Nil |
4,879 |
4 |
– |
| 100 |
5 |
30 |
25 |
33 |
54.5 million |
1.6 million |
+ |
| 100 |
5 |
30 |
25 |
66 |
4,116 |
0 |
– |
| 100 |
5 |
30 |
50 |
Nil |
9.4 million |
220,562 |
+ |
| 100 |
5 |
30 |
70 |
Nil |
24,437 |
75 |
+ |
| 100 |
5 |
30 |
80 |
Nil |
6,282 |
1 |
– |
| 100 |
5 |
45 |
25 |
66 |
19,821 |
1 |
– |
| 1,000 |
2 |
30 |
10 |
Nil |
14.8 million |
325,480 |
+ |
| 1,000 |
2 |
30 |
10 |
25 |
105,117 |
511 |
+ |
| 1,000 |
2 |
30 |
10 |
33 |
30,872 |
37 |
– |
| 1,000 |
2 |
30 |
25 |
33 |
7,370 |
0 |
– |
| 1,000 |
2 |
45 |
25 |
Nil |
48,975 |
37 |
– |
| 1,000 |
2 |
45 |
10 |
33 |
60,392 |
78 |
– |
| 1,000 |
2 |
45 |
25 |
33 |
15,471 |
0 |
– |
|
|
aNumber initially infected refers to those who are exposed during a release such that they become infectious. This excludes those who are exposed but
either do not become ill or do not become infectious.
bThe number of persons infected per infectious person is the transmission rate.
cStart day, for both quarantine and vaccination interventions, refers to the day
postrelease, with the day of release being day 1.
dQuarantine refers to removal of infectious persons only, starting on the first day of overt symptoms (i.e., rash). At a 25% daily removal rate, a cohort of
all those entering the first day of overt symptoms is entirely removed in 17 days (18 to 20 days
postincubation) after day 1 of overt symptoms, with 90%
removed in 9 days. At a 10% daily removal, a cohort of all those entering the first day of overt symptoms is entirely removed in 44 days (45 to 47 days
post incubation) after day 1 of overt symptoms, with 90% removed in 22 days. At a daily removal rate of 80%, a cohort of all those entering their first day
of overt symptoms is entirely removed in 3 days (4 to 6 days postincubation) after day 1 of overt symptoms, with 90% removed in 2 days.
eVaccination is assumed to reduce the transmission rate by a given percentage (e.g., 25% reduction results in transmission declining from 2.0 to 1.5
persons infected per infectious person, and 33% reduces transmission from 2.0 to 1.32).
f(+) = an increasing rate of daily cases on day 365, and thus the
modeled interventions will not stop the transmission of smallpox.
(–) = a decreasing rate of daily cases, such that the interventions
modeled will eventually stop the transmission of smallpox.
gNil = vaccine not used in this scenario.
|
|
| |
|
|
Table 2. Sensitivity analyses: minimum levels of intervention needed to stop transmission of smallpox by days 75, 150, and 225 postrelease |
|
| Target stop daya |
Start day of interventionsa |
No. infected per infectious
personb |
Quarantine: Minimum %
removal per dayc |
Vaccination: Minimum %
reduction in transmission (transmission rate)d |
|
| 75 |
30 |
3 |
99.4 |
Nile (3.00) |
| 75 |
30 |
3 |
Nilf |
90.5 (0.29) |
| 75 |
30 |
3 |
25 |
76.7 (0.70) |
| 75 |
30 |
3 |
50 |
56.2 (1.32) |
| 75 |
30 |
3 |
82.5 |
25.0 (2.25) |
| 75 |
30 |
2 |
25 |
58.0 (0.84) |
| 75 |
30 |
5 |
50 |
78.9 (1.06) |
| 75 |
45 |
2 |
50 |
58.5 (0.83) |
| 75 |
45 |
3 |
50 |
81.2 (0.57) |
| 150 |
30 |
3 |
63.5 |
Nile (3.00) |
| 150 |
30 |
3 |
Nilf |
80.0 (0.60) |
| 150 |
30 |
3 |
25 |
53.7 (1.39) |
| 150 |
30 |
3 |
50 |
19.7 (2.41) |
| 150 |
30 |
3 |
46.2 |
25.0 (2.25) |
| 150 |
30 |
2 |
25 |
25.8 (1.49) |
| 150 |
30 |
5 |
50 |
55.7 (2.22) |
| 150 |
45 |
2 |
50 |
Nile (2.00) |
| 150 |
45 |
3 |
50 |
33.3 (2.00) |
| 225 |
30 |
3 |
53.8 |
Nile (3.00) |
| 225 |
30 |
3 |
Nilf |
75.8 (0.73) |
| 225 |
30 |
3 |
25 |
45.2 (1.65) |
| 225 |
30 |
3 |
50 |
6.0 (2.82) |
| 225 |
30 |
3 |
38.1 |
25.0 (2.25) |
| 225 |
30 |
2 |
25 |
14.3 (1.72) |
| 225 |
30 |
5 |
50 |
46.5 (2.68) |
| 225 |
45 |
2 |
50 |
Nile (2.00) |
| 225 |
45 |
3 |
50 |
14.8 (2.56) |
|
|
aTarget stop day and start day of interventions refer to days postrelease, with day of release being day 1.
bThe number of persons infected per infectious person is the transmission rate.
cQuarantine refers to removal of infectious persons only, starting on the first day of overt symptoms (i.e., rash). Rates are the minimum rates needed,
when combined with vaccination, to ensure that there is zero transmission by the target date. With 25% daily removal rate of infectious persons, a cohort
of all those entering the first day of overt symptoms is entirely removed in 17 days (18 to 20 days postincubation) after day 1 of overt symptoms, with
90% removed in 9 days after entering overtly symptomatic period. With 50% daily removal of infectious persons, a cohort of all those entering their first
day of overt symptoms is entirely removed in 7 days (8 to 10 days postincubation) after day 1 of overt symptoms, with 90% removed in 4 days after
entering overtly symptomatic period.
dVaccination assumed to reduce the transmission rate by a given percentage (e.g., 25% reduction results in transmission decreasing from 3.0 to 2.25
persons infected per infectious person). Percentages are the minimum percentage reduction in the assumed rate of transmission needed, when combined
with quarantine, to ensure zero transmission by the target date. The resultant transmission rate, after reduction, is in parentheses.
eFor these scenarios, the assumed quarantine rate is such that the target dates can be attained without the use of vaccination.
fFor these scenarios, the assumed vaccination-induced reduction in
transmission is such that the target dates can be attained without the use of
quarantine.
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