The Hump of the Camel

During the Black Death

[t]he people of the Mediaeval Ages were uneducated about diseases and cleanliness. Many thought it was caught through the air, so they would burn incense like juniper and rosemary to try to prevent infected air. People would dunk their handkerchiefs in aromatic oils to cover their nose and mouth from the air.

But now there is Test and Trace.

At the level of public discussion, the question of vaccine passports for internal use has been a roller-coaster of rumours and about-turns, not only in the UK but across the world. Their necessity was trumpeted almost as early as the first COVID cases, and their similarity to (and potential evolution into) Internal Passports in the Soviet tradition was soon noted by opponents.

I, and others, have long been pointing out that, quite apart from the intrinsic specificity (false positive) rate of the PCR tests it has been very difficult to get hold of details on how many amplification cycles are being used in real life. The original British standard was 45 cycles (to be “on the safe side” over the WHO’s recommended 40 back last year).

OK, I refer you to another excellent post by John Dee entitled False Positive Refresher. In it he talks about the PCR test’s sensitivity (which is the nominal percentage of true cases it spots). A sensitivity of 80% means that if you test 100 sick people, it will miss 20 of them. More importantly, in this context, is the specificity (which is the nominal percentage of genuine negatives it spots). So a specificity of 99% means that if you do the test in 100 well people, it labels one as sick, ie as a false positive.