Businesses have been urged to "get prepared" for leaving the EU's single market and customs union amid concerns the disruption could hamper efforts to tackle coronavirus.
Cabinet minister Alok Sharma repeatedly failed to rule out that the supply of a coronavirus vaccine would not be affected by problems when the new arrangements come into force on January 1.
The head of British firm Croda International, which supplies a crucial ingredient in the Pfizer-BioNTech vaccine candidate, has warned that avoiding border disruption will be "a crucial step" in ensuring it is available to millions of people.
Business Secretary Alok Sharma was questioned on the issue at a Downing Street press conference.
"This is an issue... across many sectors but that is precisely why we have been investing hundreds of millions of pounds in terms of border infrastructure, and we've been investing in grants for customs intermediaries," he said.
"It's why we are making a very big effort to communicate with businesses to make sure that they are ready, so that they can get customs clearances done.
"All of that work is ongoing. If we all get prepared, we will be in absolutely the right place post-transition."
Talks on a post-Brexit trade deal are still ongoing, but even if an agreement is reached there will still be major changes to cross-border trade as the UK leaves the single market and customs union.
Mr Sharma said: "Whatever form of deal we end up with with the European Union, there are going to be changes for businesses, and my department has been writing on a weekly basis to hundreds of thousands of businesses, making them aware of individual areas where they're going to have to have a look and see whether they're ready for the end of transition.
"That may be in terms of customs clearances, it may be how they're looking to employ people who are currently working in the European Union, issues around work permits if they're going to go and work in the European Union.
"All of these issues I think businesses, of course, will want to address."
Concern about hauliers facing disruption crossing the English Channel has led the Government to introduce a permit system to enter Kent, only allowing lorries destined for the continent into the county if they have the correct paperwork.
The increased bureaucracy surrounding imports and exports has sparked fears of delays, something which can have a dramatic impact on time-sensitive goods.
Croda's chief executive Steve Foots told Sky News that the end of the Brexit transition poses a risk.
"The worry of course, the last thing we need, is a problem with a lack of an agreement, and you've got friction at the borders, and I'm sure the UK Government are acutely aware of this," he said.
"We must make sure that the vaccine doesn't have any problems getting into the UK, into the supply chain, or even the practical issues of refrigerant technologies and everything else.
"They could be products that are needed for the UK that are sourced abroad, so making sure that we are free from friction at the borders is a crucial step for the vaccine."