The Lancet article is worth a read.
https://www.thelancet.com/journals/lancet/article/PIIS0140-6...
What does their data actually show? Look at figure 2. It shows smoothly and steadily declining effectiveness that drops below zero. There is no change in the trend near the 9 month mark. How far can effectiveness actually fall? This paper stops looking after 9 months, but we know from UK data that it can in fact keep falling for much longer than that. Before they stopped reporting the numbers measured effectiveness in the UK was around -300%:
https://dailysceptic.org/archive/vaccine-effectiveness-hits-...
Additionally case rates in the boosted were higher than in unvaccinated at that point, i.e. by March 2022 COVID had become a pandemic of the vaccinated. Boosting had helped for such a short period it hardly mattered and then the problem became even worse.
Note that you have to be careful with effectiveness figures reported by public health authorities. Starting with COVID many of them began reporting "adjusted" effectiveness in addition to or entirely instead of case rates, but their adjustment methodology isn't valid.
So this is not vaccine "fear mongering". It's what government's own data shows. That makes it a very real problem that needs serious and immediate research to figure out (a) why this is happening, (b) what if anything can be done about it. The vaccines appear to have backfired and we're very lucky that Omicron is so mild. Unfortunately this will not be admitted to in the media, by governments, and not openly by researchers.
From what I could tell the The Lancet article is only talking about waning effectiveness against Covid (as previously known). [Table 1 possibly notwithstanding, but I'm reading this as people with co-morbidities are more likely to get the vaccine, not the other direction...]