Covid: Was Pfizer's vaccine rushed? Can we be certain it's safe? Our statistician answers your questions
Prof Jennifer Rogers, vice president at the Royal Statistical Society, is working with ITV News as our new Covid statistician helping us to make sense of coronavirus numbers and what they mean to you.
The Pfizer BioNTech Covid-19 vaccine has been approved by the MHRA (Medicines and Healthcare products Regulatory Agency), meaning that mass vaccination in the UK can now start.
The process from concept to approval has taken only 10 months, a process that might usually take many years.
The speed at which this vaccine has been approved has generated lots of suspicion about the reliability of the results and the safety of the vaccine.
But just how founded are these concerns?
Here, I address some of the big questions that you might be asking…
Does the fact that this vaccine has been approved so quickly mean that shortcuts have been taken?
The very simple and quick answer to this is absolutely not.
Usually, when vaccine development studies are carried out, there are many steps that are taken sequentially.
Multiple phases of clinical trials (Phase I to Phase III) need to be completed before regulators can give their approval.
They are done one after another because, for example, under normal circumstances it would be a waste of time and money to start designing a Phase III study until you knew that your Phase II study was completed successfully.
But when every day means more deaths worldwide, you are not so worried about wasting time and money and can undertake some activities simultaneously without compromising the integrity of the trial.
Normally, discussions with regulators can be a lengthy process, with to-ing and fro-ing about study design, for example, taking many months.
When all resources are concentrated onto one priority activity, that process can be sped up dramatically.
We were also told in today’s briefing that the MHRA has been carrying out a rolling review, assessing effectiveness and safety data on a continual basis, as it becomes available, rather than reviewing everything at the end.
Finally, a company wouldn’t usually consider mass producing a new vaccine until they were sure that it worked.
But companies have been taking the risk and mass-producing Covid-19 vaccines well in advance of study results, just in case they were successful.
This means that we will be able to start vaccinating vulnerable people in this country from next week.
Approval of this vaccine has taken place at record speed, but it does not mean that corners have been cut and it does not mean that all the proper procedures haven’t been carried out.
Has the vaccine been tested on enough people to be sure that it works?
When clinical trials are designed, sample size calculations are carried out to make sure that enough people are included to be able to reliably say whether a new vaccine works.
The Covid-19 vaccine trials have been no exception.
Pfizer and BioNTech calculated that if they saw a vaccine effectiveness of at least 50% on 164 Covid-19 cases, that would be enough evidence to say that their vaccine worked.
What they saw was a vaccine effectiveness of over 95% on 170 cases.
So, they definitely have enough evidence to say that this vaccine works.
No vaccine will ever be 100% effective and even the flu vaccine averages a vaccine effectiveness of 40%-60%, according to the Centers for Disease Control and Prevention.
A 95% effectiveness is excellent.
What you need to know about each vaccine:
Currently there are three different vaccines that could be approved in the coming weeks.
The University of Oxford and AstraZenica vaccine is up to 95% effective, can be stored at fridge temperature and is the cheapest, costing just £4 a dose. The UK government has ordered 100 million doses, with four million ready to go.
The Pfizer/BioNTech vaccine has up to 95% efficacy when it comes to immunisation, requires to be stored at -70C degrees and will cost £15 a dose. The UK has ordered 40 million doses, 10 million of which will be available by the end of the the year.
The Moderna vaccine is up to 94.5% effective, requires to be kept at -4C and will cost between £24 and £28 per dose. The UK has five million doses on order.
All three vaccines require two separate inoculations to be effective.
Can we be certain that the vaccine is safe?
Unfortunately, there is no such thing as zero risk. Even when you take a paracetamol, there is a risk associated.
But this vaccine has been given to over 20,000 people during the Phase III study and will have been given to even more in earlier Phases.
The two biggest side effects that were categorised as severe have been fatigue and headaches, occurring in 3.8% and 2% of participants respectively.
Professor Sir Munir Pirmohamed of the Commission on Human Medicines today said that this vaccine has a safety profile that is similar to other vaccines and that side effects are typically mild in nature and last only a day or so.
What I would also stress is that once a vaccine is approved, that is not the end of the story.
A vaccine is not just let out into the world to be administered to everyone without further surveillance.
This vaccine will continue to be studied post-approval so that we can be sure that the vaccine remains effective and monitor any future safety concerns that may arise.
How does safety testing begin?
Once a vaccine has been created and is thought to be safe to be tested on humans, trials involving volunteers can begin.
These trials are divided up into three stages and any potential vaccine must pass through them all.
Phase 1 - Different doses are given to a small number of healthy volunteers to get some idea of the appropriate dose and to ensure that the material is safe. The main purpose here is to identify the right dose for the next step in the testing process as well as rule out any major safety problems.
Phase 2 - The vaccine is administered to a larger number of people, often between 100 or 200 but sometimes in the thousands. At this stage, researchers evaluate whether the vaccine can produce a consistent immune response and monitor for potential side effects.
Phase 3 - The vaccine can be tested to measure how well it protects against natural infection. These studies often include tens of thousands of healthy volunteers to prove that the vaccine prevents the disease and identify rare problems or side effects that only show up in larger population or sample sizes. The speed of the Phase 3 trials is also dependent on the rate of infection and the R value - if infection rates are very low then the trial could drag on for months on end.
Why you can't compare vaccines but Oxford's is cause for celebration: Listen to ITV News's coronavirus podcast