Impact on current and future infection
At the start of the period beginning 24th July 2020,
the ONS community survey reported a daily incidence of 0.78/10,000
(0.4-1.49); equivalent to 4,200 new community infections each day. The
latest ONS community incidence report at the time of writing was 0.44
(at 7th August 2020). This is the equivalent to a fall
of 14%/week. Hospital admissions and deaths are falling at similar
rates. This all suggests that the underlying R-value in the population
was just above 0.8.
In the 4 weeks prior to the 13th August 2020, the
community infection admission rate, including an assumed 50% from
community infections, would then be 0.9%. The admission fatality rate
during the same period was found to be 8.2%.
Figure 1a shows graphically the impact of the different assumed R-value
(0.8, 1.0, 1.2) on the infection outcomes over the 13 weeks and the
potential cumulative numbers for both with or without face coverings for
the 3 levels of R then on infections (Figure 1b), community
hospitalisation (Figure 1c) and deaths (Figure 1d). We show, for each of
the assigned R-value, the impact of wearing face coverings in public
transport and retail environments on new infections/week, cumulate
deaths, hospital admissions and cumulative infections.
This showed, based on 4,200 new community infections/day (29,400/week),
and R-value of 0.8 (both derived from ONS data from the time of
introduction of mandatory face coverings at the end of July 2020) and a
40% effectiveness of face coverings, that the number of direct and
indirect infections associated with public transport and retail outlets
over the 3 months would be reduced from 124,000 by 11,000; a reduction
of 9%.
If the infection rate was to increase to and stayed at, 1.0 then weekly
infections would remain at 29,400 (or 382,200 over 3 months). A 40%
effective face covering worn in public transport and retail could reduce
the 3 month total by 51,000 or 13%.