Pivotal randomized control trials (RCTs) underpinning approval of Covid-19 vaccines did not set out to, and did not, test if the vaccines prevent transmission of the SARS-CoV-2 virus. Nor did the trials test if the vaccines reduce mortality risk. A review of seven phase III trials, including those for Moderna, Pfizer/BioNTech and AstraZeneca vaccines, found the criterion the vaccines were trialled against was just reduced risk of Covid-19 symptoms (read below).
There should be no secret ...