The recent change in isolation policy for people in England was based on a modelling study by Bays et al which showed that “after the 5th day after a positive test, an estimated 31% of persons remain infectious”.
Reference: Bays D, Whiteley T, Pindar M, et al. Mitigating isolation: The use of rapid antigen testing to reduce the impact of self-isolation periods. medRxiv 2021:2021.12.23.21268326. doi: 10.1101/2021.12.23.21268326
Bays et al Table 3: Percentages (rounded to integer) of people who are still infectious after each day according to their disease profile
| Day | ||||||||||||||
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 |
Still infectious (%) | 100 | 92 | 75 | 58 | 43 | 31 | 22 | 16 | 11 | 7 | 5 | 3 | 2 | 2 | 1 |
No-longer infectious (%) | 0.0 | 8 | 25 | 42 | 57 | 69 | 78 | 84 | 89 | 93 | 95 | 97 | 98 | 98 | 99 |
Bays et al Table 4: Output from the model of the effect of the
considered scenarios on disease release into the community (measured in three
different ways) and the self-isolation in addition to that which is necessary
to contain disease spread. Intervals are the 2.5 and 97.5 quantiles from the
simulations.2
|
Policy |
Released infectious (%) |
Mean time a released person
is infectious for (hours) |
Mean excess isolation per
person (hours) |
|
|
7-day isolation |
15.8%
[11.9 - 21.0] |
62.3
[56.5 - 69.2] |
76.8 [67.2 - 84.0] |
|
|
10-day isolation |
5.1%
[3.4 - 7.6] |
59.3 [53.5 - 65.6] |
141.6 [129.6 - 151.2] |
|
|
14-day isolation |
1.0%
[0.6 - 1.8] |
57.1
[51.4 - 63.1] |
235.2 [220.8 - 247.2] |
|
|
10-day isolation, or 1 negative
tests from day 7 |
9.2%
[6.5 - 12.8] |
61.1 [55.3 - 67.5] |
79.2 [69.6 - 86.4] |
|
|
10-day isolation, or 2 negative
tests from day 6 |
6.2%
[4.2 - 9.0] |
60.0
[53.9 - 66.3] |
81.6 [72.0 - 88.8] |
|
|
14-day isolation, or 2 negative
tests from day 6 |
4.1% [2.6 - 6.0] |
61.3 [55.8 - 67.7] |
69.6 [64.8 - 74.4] |
|
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