Typically, new medicines take many years before they are licensed, but if you look at the timeline for these products, there are long periods where no actual testing is being done. Much time is spent gaining approvals for each stage of the trials, finding sufficient numbers of suitable volunteers willing to take part, analysing the results of each trial stage and very importantly, obtaining funding so that development can continue
In the case of covid,virtually all of that "dead time" was removed - there was no problem finding suitable volunteers and there was no shortage of funding
So, rather than being a very much stop/go process, development of covid vaccines was very much a go/go process.
In addition, in the UK, the JVCI was continually monitoring the trials and had ongoing results, This meant that they did not have to spend a large amount of time analaysing all of the trial results at the end of the process and thus cause further delays before the vaccines were given a temporary licence.
Covid is a SARS virus and that helped the fast developement of the Astra Zeneca vaccine because they already had a "tool kit" of basic vaccines already developed and only had to fit the "right sized spanner" into the tool box to make an effective vaccine.
In fact the structure of the Astra Zeneca vaccine was figured out over a single weekend and the chemicals required to make ordered on the Monday morning
This makes interesting reading
Good fortune and scientific brilliance were behind the Covid-19 vaccine being developed so quickly.
www.bbc.co.uk
Science should always be questioned, and scientists question it more than anyone else - coz that's how science works
Science denial is another thing altogether.
Cheers
Bruce