Up to 2,000 “irreplaceable” people working to supply the UK with coronavirus vaccines are to be prioritised for jabs, the government has announced.

The aim is to protect “highly trained” workers, including at vaccine manufacturers Pfizer and AstraZeneca (AZ), who have been identified as “crucial” to the delivery of the jabs to the population.

The Department for Health and Social Care (DHSC) made the announcement after AZ called for vaccine supply workers to be inoculated and revealed the company had suffered an outbreak.

It came amid an apparent slowdown of vaccinations in England, with 170,900 doses administered on Monday, short of the number needed to achieve a target of two million a week and far below last week’s figures, which twice rose above 310,000 a day.

DHSC sources said vaccinations had not been slowed down by Covid outbreaks in the supply chain.

But the department said that jabbing key staff would “reduce the risk of an outbreak that would disrupt the immediate supply chain, which could have a significant impact on the largest vaccination programme in British history”.

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A separate senior government source said people should expect supplies to be “lumpy and bumpy” and that the best judge of the speed of the rollout was the seven day weekly average number of jabs.

“We’ll distribute as many doses as are delivered,” they said.

“Things will move around from day-to-day.”

The government is also expecting the number of vaccinations to rise again towards the end of the week as more supplies come in from AZ.

Last week, Mene Pangalos, AZ’s executive vice president of biopharmaceuticals research and development, said he was “worried” about maintaining a continuous supply of the vaccine his firm has developed with Oxford University.

“Of course, with the outbreak and the pandemic where it is – I feel it’s critical [that] the people that are working on this vaccine are actually immunised,” he told the Commons science committee.

“Because if you have an outbreak at one of the centres – which we’ve had actually – or in one of the groups in Oxford [that] is working on new variants, or the people that are working on the regulatory files – everything stops.

“This is a concern that I have and so again we’re pushing to try and get our key workers that are working on the vaccine project immunised to try and prevent these outbreaks.”

The workers to be prioritised for jabs include those making the vaccine substance, others working on so-called “fill and finish” and batch testing, as well as those responsible for getting doses to the “right place at the right time”.

Some workers at sites such as Oxford BioMedica, which manufactures and tests the bulk of the UK’s AstraZeneca supply, will be eligible, and some staff at Wockhardt involved in fill and finish will also be included.

Eligible workers will be identified by their employer against government criteria and the most appropriate location for vaccination would be agreed between the NHS, local providers and employers.

This has been agreed by all four nations and will be implemented across the UK.