The two are related. The unknown is how the relationship we’ve seen so far will be affected by vaccination results.
I’m open to suggestions about what the right threshold should be, but basing the decision on prevalence over time seems the right way round to me.
One of the major problem with insisting on that approach is the thorny issue of 'false positives',
which isn't that much of a problem when prevalence is high, as they effectively get drowned out
by the tens of thousands of genuine positive results, but if virus prevalence was to fall significantly,
as it did last Summer, the situation is reversed and the false positives become dominant.
Specifically, it's thought that somewhere between 98% and 99% of positive PCR results are 'true' positives,
but even if we are generous and assume that the figure is as high as 99.5%, that still means that 0.5% are
false positives, so
on a day when 700,000 tests are performed, that means that at least 3,500 are
false positives, even if the number of actual 'cases' on that day is zero!!
In other words, while it should be possible to get genuine cases under 1000 per day later in the year as per
Hunt's statement, it will be impossible to
prove that they are at that level because of the statistically flawed
nature of the PCR test in a low prevalence environment.
This is the main reason why 'zero covid' is a ridiculous pipe dream - because there is absolutely
no way of knowing for sure that there are less than 3,500 cases, never mind zero!!
MARK