https://www.thelancet.com/journals/lanepe/article/PIIS2666-7...

... but who's right?

If vaccines really affected transmission a lot, we'd see it in drastically reduced case numbers. What we actually see is that post-vaccination case numbers reach record highs. That should be a pretty basic reality check on any claims that transmission is heavily affected. Either that, or you have to believe transmissibility has no impact on case numbers.

What you tend to see is that studies that are older or use older data conclude more effectiveness. The New Scientist article you cite presents evidence from a study that used data only pre-Delta. But the point people are making when they say it doesn't affect transmission is about the current state of play. Not the situation back in March two major mutations ago.

You can deploy as many non-sequiturs and specious arguments in service of the view you cling to, but the evidence remains the same.