Travellers returning to England from Spain's Balearic Islands from next week will have to go into quarantine at home unless they are fully vaccinated.
This follows a change in policy that could spell bad news for young holidaymakers who have not yet had both vaccination shots.
Britain has one of the fastest inoculation programmes in the world but the UK government has effectively prevented travel to most countries through quarantine and testing rules.
It is slowly lifting these restrictions and from July 19 it will allow fully vaccinated passengers to travel to all countries except those with the highest Covid-19 risk, which are on a government red list.
After a travel review, UK Transport Secretary Grant Shapps said the Spanish islands of Ibiza, Majorca and Minorca had been added to the amber list for travel. This means that those younger adults who are not fully vaccinated would have to go into quarantine at home for 10 days.
Mr Shapps said the status of the islands changed owing to a sharp rise in cases. The British Virgin Islands were also moved to amber.
The government also put Cuba, Indonesia, Myanmar and Sierra Leone on its red list, meaning anyone travelling from there would need to quarantine in a hotel.
"Travel continues to be different from usual, and passengers should check the latest travel advice from the Foreign Office and be prepared for longer wait times and more checks during their journey," the government said.
Britain is adding Hong Kong and Bulgaria to its green list. Croatia and Taiwan will move to the green list from 19 July.