Grimsby’s Novartis plant has been granted a 12-month stay of execution.
Production of two of the key drugs the global pharmaceutical giant manufactures on the South Humber Bank is required for a further year.
The company said demand has increased as health authority approvals on manufacturing are awaited elsewhere.
It means two of the three buildings - and a large proportion of the staff - will now be retained throughout 2021, having been scheduled to close at the end of this year.
It will be seen as a huge short-term boost to the local economy, retaining a high-skilled site, as the wake left by the coronavirus pandemic is expected to lead to immediate recession.
The huge plant employed 400 people when the axe fell back in September 2018, with salaries alone pumping £23 million into the area.
The first phase of redundancies has been between January and June, with numbers described as in their dozens.
A first production run ended on Monday, with the last batch from Building 110. Buildings 120 and 150 will now continue for a further 18 months, with site power, warehousing and maintenance staff also retained to a level now being determined.
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Ian Johnson, managing director, said: “The site will remain operational through 2021, making the two products. This change in the production timeline will require some roles longer, particularly in direct production, quality control, safety and the like. We are working through that now.
“The actual decision to exit the Grimsby site remains unchanged, it is just the timeline. It has been revised because of the two products.”
The extension means the 229-acre Moody Lane site will now see in 70 years of continuous operations, having been originally established in 1951.
In the year the closure was announced turnover leapt 12.3 per cent to £158.4 million with profits of £6.5 million sent to Switzerland.
Throughout the period the management have been clear productivity hasn’t been the reasoning, with a switch in global strategy to tailored medicines behind the closure.
A taskforce has been formed, including MPs, local government and business figures.
Coronavirus hasn’t stopped production, with Mr Johnson full of praise for the employees and contractors in dealing with the measures brought in.
The site is being marketed for sale, and agents have now been briefed on the extension.