I can't find any source in there suggesting a lack of effectiveness. The underlying source linked by the article mentions a reduction of 80% in symptomatic disease, which is responsible for most transmission. I can't find anything very recent, but here's an analysis that takes Delta into account:

https://assets.publishing.service.gov.uk/government/uploads/...

Finding 80+% protection against symptomatic disease and ~40% reduction in onwards transmission, from three different modelling groups.