Public health expert Dr Gabriel Scally has said he is 'very confident' of the safety procedures around any coronavirus vaccine.
It comes after Britain became the first western country to approve the use of a vaccine, giving the green light for people to start receiving the Pfizer/BioNTech jabs.
It is expected an immunisation programme could start as early as next week, with residents and staff in care homes to be prioritised.
Dr Scally told The Pat Kenny Show the fact that the UK is first does not mean much.
"It's who finishes the race well that counts, not who's first out of the blocks, and it'll depend on vaccine supply and it does take time.
"The fact that you need two doses means that it is going to take two months before someone who has two doses of the vaccine will be properly immuniszed".
On safety, he said he has no doubt that the issue is paramount for all of the regulators.
"The safety processes have not been cut short on these vaccines, and I'm very, very confident about them.
"And very, very confident in the regulatory processes - whether it be in the UK's process, the European Union's or the American process: it will be properly scrutinsed".
He said transparency is important, and the drug companies should put their data out to the public.
"I personally think it's a bit odd that when I buy something in a supermarket - some manufactured food - there'll be a full list of ingredients on it.
"But there isn't a full list of ingredients on medicines.
"I think all of that transparency stuff should be absolutely seen openly by everyone".
Vaccine 'to dig UK out of a terrible hole'
He said Britain has got to the post first, as they backed several different drugs.
"Britain's always had a very strong pharmaceutical regulatory process and healthcare regulatory process, so it can move very fast.
"One of the things that has made this whole process fast is that there has been a lot of money put into it by governments, by the EU and World Health Organisation and so on".
He also said Britain took out options "on a quite a number of vaccines - backing all the main horses in the race."
Dr Scally said this is just as well, as "the vaccine is going to dig them out of a terrible hole."
"You'll know the UK's performance in terms of COVID-19 has been appalling, shambolic and they really need to make sure that this works well."
"They've got nothing left in their powder store anymore because things are not going well on hardly any front to do with the virus".
Dr Scally added that it is important the vaccine is distributed based on need, not wealth.
"One of the impressive things I think has been the WHO programme for vaccine sharing across the world.
"The WHO has been fantastic in trying to ensure that it isn't a rich person's vaccine - that this vaccine will be shared with the countries on the basis of need, and I think that's tremendously important".