UK residents fully vaccinated against Covid-19 are allowed to enter Malta without quarantine. At least in theory, because if you have been vaccinated with the AstraZeneca vaccine, your holiday trip can end at the gate in the UK.
The reason for this is that there are two different variants of this vaccine. The one that is produced in Europe is known under the brand name Vaxzevria and is approved by the EMA. If you have received both stitches and at least 14 days have passed, you can enter Malta without any problems.
In the UK, however, the Indian licensed production is also administered to Covishield. This has a UK emergency approval, but none from the EMA. And that is exactly a problem, because British Airways, for example, has already refused to board British passengers who have been vaccinated with the “Indian variant” on Malta flights.
An unclear formulation on the part of the Maltese government is likely to be the main cause, because the official documents only mention AstraZeneca. The Ministry of Health has not specified which of the two variants is meant exactly. On top of that, British travelers can only tell from the batch number whether they have received Vaxzevria or the licensed production Covishield. British Airways appears to have researched this carefully and trained the staff accordingly.