The UK has re-introduced compulsory pre-departure tests for all travellers entering the country amid fears of the spread of the omicron variant of the coronavirus.

The UK government said on Saturday that new analysis conducted by the UK Health and Security Agency (UKHSA) indicated that the window between infection and infectiousness may be shorter for the omicron variant, which increases the efficacy of pre-departure testing as it is more likely to identify positive cases before travel.

Therefore, starting Tuesday morning, anyone arriving in the UK is required to provide a pre-booked negative polymerase chain reaction (PCR) or lateral flow test — taken no earlier than 48 hours before departure. This also applies to vaccinated passengers and children aged 12 and above.

“We knew this winter would be challenging but the arrival of a new variant means we must further strengthen our defences,” said UK health secretary Sajid Javid.

“As our world-leading scientists continue to understand more about the omicron variant we are taking decisive action to protect public health and the progress of our Covid-19 vaccination programme. I urge everyone to do their bit to slow the spread by following the new travel rules, wearing masks where mandatory and most importantly getting the booster jab when called,” he said.

Under current rules, travellers only needed to self-isolate until they test negative within two days of arrival. Scientists have raised concerns that the heavily mutated omicron variant may be more transmissible than the dominant delta strain. The UK Department of Health and Social Care (DHSC) said that in light of the emerging evidence and the changing global picture with regards to the spread of omicron, airlines would be required to check for pre-departure tests alongside the completed passenger locator form, and passengers will not be allowed to board a flight without providing evidence of a negative test result.

Given the reduced incubation period of the omicron variant, passengers are advised to take the pre-departure test as close as possible to their scheduled departure to the UK and no earlier than 48 hours before travelling, the DHSC said.

From 4am on Monday all UK and Irish citizens and residents arriving from Nigeria must isolate in a government-approved managed quarantine hotel facility for 10 days, and receive two negative PCR tests.