Actually not a surprise at all. The sceptics have been saying this all along that there has yet to be an effective vaccine against a coronavirus. For example, take the common cold, some of which are caused by a coronavirus. If you get a cold, your immune system will respond (better response than from a vaccine) and you will be immune from another similar infection for a while. Then you will catch another cold because there appears to be no such thing as permanent immunity against a coronavirus.
So recently in the UK, data has been published on the dwindling immunity from vaccination after 4 and 6 months. And vaccine stocks have been ordered to give everybody a booster shot. And doubtless the same will be done every 6 months, ad nauseam. This really is not a good answer, but is a very expensive one.
It has been shown that natural immunity conveyed by getting the disease and recovering is many times better than any immunity given by vaccines. So the only sensible way ahead is to treat the disease so that those who catch it stay alive and out of hospital. They will then have good immunity against reinfection for a while.
Fortunately, not all the available vaccines use untested mRNA technology. I believe the Oxford Astra-Zeneca and Johnson & Johnson vaccines to be more conventional, but I hear there is a possibility that Astra-Zeneca will withdraw from the market.