>Huh? Checking if the vaccine does anything at all is after the design is done. The choice of when to test symptoms vs. spreading is more about difficulty of getting the data than anything else.
You're the one arguing in bad faith, demanding evidence of a negative. When the vaccines were released, the published testing only covered a few key endpoints - primarily, incidences of lab-tested Covid cases. Any work on measuring effects on transmission was done by 3rd parties (in this case, I believe it was researchers in Israel).
Covid has a very specific (and small) risk profile. That's the idea we were all sold - vaccinate the vulnerable, get on with our lives. Given that it presents very little risk to the vast majority of people, it doesn't really matter about transmission. Except that is, now we are apparently trying to surpress potential mutations, which means we'll be battling a relatively harmelss (compared to the great pandemics of the past) disease forever.