Initial real world evidence for lower transmissibility of (Pfizer) vaccinated individuals (from Israel)

Since the vaccine was rolled out to over-60s first, starting Dec 20, they just compared the viral loads from PCR tests of over-60s with those of 40-60 year olds. Until Jan 15th there wasn't much difference, then there was. They estimate a 1.6-20x reduction in viral load (1.6-2.6 in PCR cycle threshold) after a single dose of the Pfizer vaccine.

Paper

Two things I don't get:

- if the Israeli databases are so great, why just stratify by age? (ie why not match test results to vaccination status?)

- the relationship between cycle threshold and viral load. (I thought the relationship was: 2^Ct ~ viral load, but that's not consistent with the figures reported).

Anyway, to the people who keep saying there's no evidence vaccination reduces Covid transmissibility: NOW THERE IS