The group that did
the Santa Clara, CA
antibody test, have run
another test on 5,600
baseball employees,
and this time found
only 0.7% carry
COVID-19
antibodies.
This result suggests
the US is a long way
from "herd Immunity".
Of the 5,603 major league
employees who submitted
to what researchers called
the largest national antibody
study to date, only 60 tested
positive.
The researchers
announced an
estimated positive
rate of 0.72%,
after adjusting results
for what they said were
false positives and
false negatives.
This test is still
not random.
The adjustments
are still large.
The earlier Santa Clara
California test
found 1.5% of those
who answered an ad
carried antibodies
to COVID-19 in that
high risk county.
The authors "adjusted"
that raw number to 3% to 4%,
which received criticism
here and elsewhere.
Maybe responding to
the criticisms of their
first study, they adjusted
the actual 1.1% result
this time down to 0.7%
to compensate for
the false positive rate.
Most of the antibody studies
draw on higher high risk
people in higher risk areas.
People with no symptoms
are likely to stay away.
This study had more
white men aged under 65.
The infection rate is so low
it in the same range
as the false positives
(around 0.5%).
With a 1% antibody rate,
half the positive tests
may be false.
That would not be
much help to employers
or employees looking to
get people back to work.
They only have
a 50:50 chance
the test is right.
The message here is that
99% of this group
had not been infected
by COVID-19.