As of today 7 January 2022 Scotland has joined England, Wales and Northern Ireland in dropping for fully-vaccinated persons and those under 18 the requirement to take a pre-departure COVID-19 test and upon arrival self-isolate until a negative result is received.
Visitors to the UK will still be required to take a COVID-19 test within 2 days of arrival. But beginning 9 January, this can be a lower-cost lateral-flow test. Those who receive a positive result from this test must then take a PCR test and self-isolate until a negative result is received.
Ireland has also dropped the requirement for fully-vaccinated visitors to produce a negative test result before entering. But unvaccinated persons must still show a negative result of a PCR test taken within 72 hours pr-arrival.
These changes should effectively normalize travel in the Common Travel Area, and restore the vital UK market for Ireland tourism.