Following months of rigorous clinical trials,

the Pfizer/biontech Covid-19 vaccine has been approved for use in the UK and arrives this week. But key questions remain and our panel of medical experts – made up of deputy chief medical officer Professor Jonathan Van-tam, Chief Executive of the Medicines and Healthcare products Regulatory Agency Dr June Raine CBE and Head of Immunisations at Public Health England Dr Mary Ramsay – are here to answer them Vaccines usually take years to develop, so how can the Covid-19 vaccination be safe if it’s ready in months?

Professor Van-tam: These vaccines have been through phase one, phase two and phase three, just like ordinary vaccines. With the Pfizer vaccine, I think the total clinical trial size is something like 45,000; the Astrazeneca results so far reported are based on just over 24,000 volunteers – there’s at least another 10,000 to follow, and the number size for Moderna is very similar. These are very, very big studies. The numbers involved were essentially the same as you’d expect for a normal peacetime vaccine, and on top of that the safety assessments and the assessments of effectiveness at the end are the same.

Dr Raine: As Covid-19 is a public health emergency, scientific evaluation and approval is being done in the shortest time possible while complying with established and robust safety, quality and effectiveness standards. Safety is our watchword. Everyone can be absolutely clear that the standards that need to be met, will be met.”

How have you decided who gets the vaccine first?

Dr Ramsay: We looked at a lot of data showing who was getting infection and who was dying from infection. The primary thing the Joint Committee on Vaccination and Immunisation (JCVI) looked at was death rates by age, by clinical factors, and by any other factors that GPS could measure, such as deprivation, geography or ethnicity.

It’s very clear the death rate is much higher as you get older, particularly over 75. That’s why we’re prioritising people in older age groups, then coming down in age, picking up people who are clinically vulnerable and those who have underlying conditions along the way. Those working in health and social care will be high on the list as well. The same goes for care home workers.

Will the vaccine prevent disease or just reduce symptoms?

Professor Van-tam: If you’re going to prevent transmission you need a vaccine that is taking out the illness and also the asymptomatic infections. There are some signs from Astrazeneca that this might be the case.

That does not mean the other vaccines where results have already been announced or that are or are still in development, don’t also reduce transmission; it’s just we don’t know at this point in time.

Are there any side effects?

Dr Ramsay: All the side effects are predictable – the kind of thing you get with other vaccines: a sore arm, bit of a temperature or feeling a bit fatigued.

How will the vaccine be rolled out?

Dr Ramsay: I think there’s going to be a lot of different models used because, for example, with elderly, frail people they’re clearly not going to drive to the nearest centre – you might have to take vaccine to them in their home.

The hospitals will probably be doing their staff, then there will potentially be these vaccination sites which will probably be more important for the younger population who can drive.

Is there anyone who shouldn’t have it?

Dr Ramsay: A reason to defer a vaccination is being pregnant – that’s just being precautionary. We don’t expect there to be a problem, but without having the vaccine tested on pregnant women we’ll probably recommend they wait until after they’ve had the baby.

Similarly, it hasn’t been tested in children, although a teenager would probably respond similarly to a young adult so they could likely have the vaccine.

How long will it take to immunise as many people as is needed for us to return to normal life?

Dr Ramsay: A normal flu programme will immunise about 15 million people in up to three months. We need enough vaccine – that’s the key issue – and the ones so far all involve two doses.

For the first phase of 30 million people, we’re talking about 60 million vaccines.

The NHS is going to bring in more staff so we hope we can do it quickly, but we’re talking several months before we’re really at the point of getting a large proportion of the public immunised.

And until we really know how the vaccine is working and how long the protection lasts, it’s very hard to predict when we’ll be back to normal life.