The coronavirus vaccine has been offered to everyone in the top four priority groups in the UK, the government has said after meeting its initial target in the roll-out of the jab.

Prime Minister Boris Johnson had set a deadline of Monday 15 February to offer a first dose of the COVID-19 vaccine to all older care home residents and staff, everyone over 70, all frontline NHS and care staff, and those who are clinically extremely vulnerable.

After achieving that target, ministers have set their sights on offering the vaccine to everyone over the age of 50 and all adults in at-risk groups – amounting to 32 million people – by May.

But how realistic is that aim?

More than 15 million people in the UK have received a first dose since 8 December, making the roll-out of the jab in this country one of the fastest in the world.

Scroll down the chart to see the milestones in the vaccine roll-out so far.

8 December: 90-year-old Margaret Keenan becomes the first person in the world to receive the Pfizer–BioNTech vaccine, outside of clinical trials.

The following week more than half a million people in the UK receive their first dose but supply problems slow the rate for the rest of the month.

The roll-out of AstraZeneca’s easy-to-distribute vaccine begins on 4 January, leading to an almost three-fold increase in doses the following week.

By mid-January health and social care workers begin receiving their first doses from more than 1,000 locations around the UK.

2,532,381 doses are given in the seven days to 24 January – the highest in a single week. Half of people aged over 80 have received their first vaccination by this time.

On 15 February, the UK government says it has offered a vaccination to everyone in the top four priority groups, achieving its target. One in four adults have now received a first dose.

While everyone in the top four priority groups has been offered a first dose, what proportion of people in older age groups have received the vaccine?

The table below reveals the percentage of older age groups who have been given a first dose of the COVID-19 vaccine in different regions across the UK up to 7 February, except Northern Ireland where the data is not available.

The figures are published weekly and the data for the last week has not been released yet.

The government has now set a target to offer a first dose of the vaccine to all 32 million people in the top nine priority groups by May.

This covers everyone over the age of 50 and younger people considered clinically vulnerable.

But is it likely to meet that target? We have considered three scenarios.

The government’s next target is to offer the first dose to a further 17 million people by May, in time for the local elections.

If vaccinations continue at the current rate and second doses are given at 11 weeks, all 32 million people in the nine priority groups could receive a first dose as soon as the end of March.

If the daily vaccination rate dropped by around 5%, as it did in late January when the supply of the Pfizer vaccine dipped, then the target could be met by 4 April.

But if the addition of the Moderna vaccine helped to increase the daily rate by a similar amount, 5%, the government could offer a first vaccine dose to all 32 million people by 25 March.

The analysis above has been calculated using the most recent 14-day daily vaccination rate and assumes that people requiring a second jab are given it at 11 weeks.

But they are just a few scenarios of how the government might reach its next target.

There are many factors that could affect progress of the roll-out, some beyond the control of minsters, like vaccine supply.

Disruption to production or distribution could slow the process but the addition of the Moderna jab, due before spring, could boost it.

The number of vaccination centres and staff are also limiting factors, which prompted Labour labour Sir Keir Starmer to call for jabs to be recommended “round the clock”.

If this happened, it could speed up the process considerably.

Finally, the timing of the second dose could have a significant impact.

If people already given a first dose do not receive their second one until the 12-week deadline, it will ease the pressure on supply and distribution.

Similarly, if second doses were offered at 10 weeks then this could increase demand so much the May deadline would become problematic.

Methodology: Daily dose rate between 30 Dec to 10 Jan, for which data isn’t available, uses average doses derived from 1.6 million total doses assumed over the same period.

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