Also not a biologist, but on the point of vaccines and whether they prevent the disease full-stop or just reduce the risk of serious illness, that's covered in the article.
My synopsis of that was that it was not expected (by the developers of the vaccines) that it would prevent people getting the illness, but that it would considerably reduce the risk of serious infection.
Some early trial results raised hopes that it would prevent people getting it, but with Delta that's not been borne out.
That said, in addition to reducing the risk of serious cases, it does also help reduce transmission as vaccinated people who get it, generally have less serious cases, which mean they are infectious for a smaller amount of time.
My synopsis of that was that it was not expected (by the developers of the vaccines) that it would prevent people getting the illness, but that it would considerably reduce the risk of serious infection.
Some early trial results raised hopes that it would prevent people getting it, but with Delta that's not been borne out.
That said, in addition to reducing the risk of serious cases, it does also help reduce transmission as vaccinated people who get it, generally have less serious cases, which mean they are infectious for a smaller amount of time.