Vaccine-resistant variant But both Ireland and the UK will have a mutual weak spot in the form of the Northern Irish Border and the Common Travel Area more generally. This will be very difficult to shut for more than a very short period of time â if at all. And if a vaccine-resistant variant enters one country, it will be very difficult to avoid it spreading to the other. This means that there can be no going it alone for either country. A two-island border quarantine policy, with a jointly agreed policy on quarantines for travellers entering from outside the two countries, could protect against new variants entering from overseas.