British regulators have become the first to authorise the Covid-19 vaccine developed by American drugmaker Pfizer and Germany’s BioNTech for emergency use. Because trials of the vaccine have shown it has 95 per cent efficacy, there is acute interest in how the United Kingdom plans to implement potentially its biggest-ever immunisation programme.

Here’s a look at what is known about Britain’s vaccination plan:

How much of the vaccine does the UK have?

Not enough. The UK has put in orders for 40 million doses, which can inoculate 20 million people, since each person gets two doses 21 days apart. Other vaccines will be needed for all the 53 million or so people eligible for shots; the UK only plans to immunise the population over age 16.

When will the rollout begin?

The plan is to start a phased rollout of the Pfizer/BioNTech vaccine early next week across the UK, including from 50 “hospital hubs” in England. Around 800,000 doses are slated to arrive from Belgium in the coming days.

The aim is for the bulk of the first deliveries to be used on the most “at-risk” groups — nursing home residents and their caregivers, as well as people over age 80. The National Health Service (NHS) will take the lead in the rollout of the vaccine, which eventually will expand to pharmacies and specially built vaccination centers.

How will the rollout work?

It won’t be straightforward. Because the vaccine must be stored and transported at about minus 70 degrees Celsius, there are clear logistical issues. Fortunately, the vaccine is stable at normal refrigerator temperatures, between 2 and 8 degrees Celsiu, for a few days, meaning that it can be stored locally ahead of being administered.

Another complication arises from doses coming in packs of 975 that cannot be divided at the moment, making it impossible to deliver vaccines to individual care homes. NHS England Chief Executive Simon Stevens said he hoped authorities will approve a safe way of splitting up the dose packs so the jabs can get to care homes this month in the “first tranche of priorities.”

How long will the vaccination effort take?

Months. The British government aims to have the most vulnerable sections of the population vaccinated by April. Because the UK won’t have enough of the Pfizer/BioNTech vaccine, it will need other ones.

Two candidates are currently being assessed. The one from American biotechnology company Moderna had similar efficacy rates as Pfizer/BioNTech’s. Another vaccine from the University of Oxford and British pharmaceutical company AstraZeneca had a lower efficacy rate but is the cheapest. Britain has bought 100 million doses of the Oxford vaccine.

If approved, it is widely expected to be used on people who are not in the vulnerable groups listed in the first phase of Britain’s immunisation programme.

Will the UK make vaccines compulsory?

No. Taking the vaccine will be voluntary, but the government and public health bodies are strongly urging everyone to get it. There will be no specific precautions required for anyone who has already had Covid-19, and there will be no mandatory testing for the virus.

Who will be vaccinated first?

The most vulnerable.

The independent Joint Committee on Vaccination and Immunisation (JCVI), which advises the British government, said those most at risk of dying from Covid-19 should be top of the priority list. So elderly people in nursing homes and their caregivers will be the first priority, followed by people aged over 80 and front-line health workers.

Who is next?

All residents 75 and older should be vaccinated next, according to the JCVI, followed by those age 70 and over and people deemed to be clinically “extremely vulnerable".

During the first phase of the immunisation programme, Britain has created nine separate groups down to those age 50 and above. Overall, it hopes that between 90-99pc of people most at risk of dying from Covid-19 will have been immunised during the first phase.

Is the vaccination plan set in stone?

No. The JCVI acknowledged that the scale of the vaccination programme is unprecedented and that flexibility will be required, not least in how to transport the vaccine to care homes.

What about access for other hard-hit groups?

As the rollout gathers steam, the JCVI is also advising local NHS providers, public health teams and community leaders to keep an eye out for any potential health inequalities linked to ethnicity, deprivation or access to health care.

Studies have shown a disproportionate number of people from poorer households and from ethnic minorities have died during Britain’s coronavirus outbreak. The UK has seen nearly 60,000 virus-related deaths, Europe’s highest death toll in the pandemic.

How long before immunity kicks in?

Within a month. Data from the vaccine trials, which involved more than 40,000 people around the world, show a similar immune response, irrespective of age, race or country the volunteers lived in.

Partial immunity does occur after the first dose, but British regulators expect people to become immune about seven days after the second dose. It is not yet exactly clear how long that immunity lasts.

What's the long-term plan?

There are a number of answers that will only emerge through the test of time, such as its impact on transmission rates. It’s also not clear how long immunity will last and whether people will need an annual dose of the vaccine, as with the flu vaccine. The UK will set up a monitoring programme, whereby people will be asked to help build up knowledge.

First up will be side-effects. They are expected to be modest, lasting a day or so and equivalent to those after other vaccines.

What about the anti-vaxxers?

Britain’s Medicines and Healthcare Products Regulatory Agency, which authorised the Pfizer-BioNTech vaccine, insists no corners were cut in the process and that the experience of the rollout will show that the vaccine is safe and effective. The government has also indicated it will seek to stem misinformation and is thought to be actively recruiting well-respected people to front a national immunisation ad campaign.