Wockhardt UK Ltd has carried out the "fill and finish" stage of AstraZeneca vaccine production at its Wrexham plant since 2020.
Staffing levels were increased to about 500 during the vaccination rollout.
However the company said the workforce would return to a "normal" pre-Covid level when its current UK government contract ends this month.
The factory was seen as a crucial part of the government's mass-vaccination programme and has been visited by Prime Minister and the Prince of Wales during the pandemic.
However the Oxford-AstraZeneca vaccine was not used for third booster jabs.
The company said it aimed to minimise the impact of job cuts.
"We scaled up at speed to meet the urgent need to supply the vaccine, including investing and recruiting where needed to meet this demanding deadline," it said in a statement.
"This has been an unprecedented period in our sterile injectable history and we have not been operating under normal manufacturing timescales or workforce numbers.
"We therefore have made the difficult decision to now undertake a process to 'right size' our business to anticipate and meet the future needs of the organisation without the vaccine work.
"Wockhardt will continue to operate as normal manufacturing all other product lines including critical medicines into the NHS."