MSD's Irish footprint has been quietly growing for years, with Carlow at the centre of it, but the biggest move yet landed in January 2025: a deal to buy a vaccine manufacturing plant in Dundalk, Co Louth, for more than €500 million. It was the clearest signal yet that MSD sees Ireland, and its established base in Carlow, as central to its global vaccines strategy for years to come.
Carlow: the long-running anchor site
MSD Carlow opened in 2008 as the company's first vaccines facility outside the United States and has grown steadily ever since. The 200,000 square foot site fills and supplies vaccines, biologics and small molecule drug products for patients around the world, and has become one of the biggest employers in Ireland's south-east.
In 2022 MSD confirmed a new, first-of-its-kind facility at Carlow focused on next-generation oncology biologics, creating over 100 permanent roles on top of 700 construction jobs. That facility, together with a new biologics plant in Dunboyne, Co Meath, officially opened in September 2023 as part of a combined investment of more than €1 billion, adding 670 jobs and pushing MSD's total Irish headcount past 3,100 people.
The 2025 Dundalk acquisition
MSD kept building on that momentum. On 6 January 2025 the company announced it had agreed to acquire the WuXi Vaccines manufacturing facility in Dundalk, Co Louth, in a deal worth over €500 million, according to MSD Ireland's own announcement and reporting by the Irish Times and RTE.
The Dundalk site is a 15,520 square metre, three-storey plant offering drug substance manufacturing, drug product manufacturing and quality control laboratories, and had been operating under a 20-year vaccine supply contract with MSD since it first opened. Roughly 200 people were already working there at the time of the deal, and MSD said it planned to add a further 150 jobs at the site over the following year.
The acquisition brought MSD's Irish footprint to eight locations across Carlow, Cork, Dublin, Louth, Meath and Tipperary, and came on top of roughly €3 billion the company had already invested in Ireland over the previous three years.
MSD's own announcement described Dundalk as the first facility in its Irish network dedicated specifically to vaccines, and said the site would focus initially on qualification and continued product development as MSD took over from WuXi, rather than an immediate ramp-up to full commercial output [MSD Ireland](https://msd-ireland.com/news/msd-ireland-announces-acquisition-of-wuxi-vaccines-dundalk-site/). MSD and WuXi had in fact been collaborating at the Dundalk site since 2019, so the 2025 deal formalised a relationship that already stretched back several years rather than starting cold.
A 1,000-job growth plan
Alongside the Dundalk deal, MSD Ireland said it was planning to add approximately 1,000 new jobs across its expanded Irish network over the following year, spanning all eight sites rather than being concentrated in a single location.
Sanat Chattopadhyay, president of MSD's manufacturing division, said the company's manufacturing footprint in Ireland was 'unparalleled' and that he was 'proud to oversee its continuous expansion,' while Samantha Humphreys, managing director of MSD Ireland Human Health, credited the company's roughly 3,000-strong existing workforce for helping secure the new investment. Taoiseach Micheál Martin described the Dundalk takeover as 'a tremendous vote of confidence' in the town, according to the Irish Independent.
The Dundalk site gives MSD its only live-virus vaccine manufacturing facility in Ireland, complementing Carlow's role in filling and supplying a broader range of vaccines and biologics, and adding a distinct capability to the company's Irish network rather than duplicating it.
MSD's careers material describes Dundalk as 'the latest addition to the Ireland manufacturing network' and the first site in the group focused purely on vaccines, sitting alongside Ballydine, Brinny, Carlow, Dunboyne and MSD Biotech in Dublin as part of a network now employing around 3,600 people across the country according to the company's own figures published in early 2026.
That workforce figure has kept climbing through 2025 and 2026 as MSD has continued recruiting across its network, a trend the company points to as evidence that its Irish investment plans are translating into real jobs rather than remaining announcements on paper.
How the plan is playing out
The handover of the Dundalk site from WuXi to MSD was targeted for completion in the first half of 2025, giving MSD control of a fully operational, already-staffed facility rather than a greenfield build, a faster route to adding vaccine manufacturing capacity than constructing a new plant from scratch.
Combined with the Carlow oncology biologics facility and the Dunboyne biologics site that both came on stream in 2023, MSD's Irish operations now span vaccines, biologics and small molecule manufacturing across three counties, with recruitment continuing through 2025 and into 2026 as the 1,000-job target is worked through.
By mid-2026, MSD was advertising senior leadership roles at Dundalk itself, including an Operations Director for drug product and drug substance manufacturing to sit on the site's leadership team and steer the plant through technology transfer and towards full commercial-scale vaccine production, a sign the site is moving from handover into the more demanding work of building a stable, qualified manufacturing operation.
That pattern, hiring senior operational and quality leadership well before a newly acquired plant reaches full output, mirrors how MSD approached its Carlow and Dunboyne biologics facilities in the run-up to their 2023 opening, and points to Dundalk reaching fuller commercial vaccine production over the following one to two years rather than an overnight switch-on.
MSD has also kept framing Dundalk's progress within the context of its wider Irish network: the company's careers material notes that its Irish operations now span vaccines, biologics, small molecules and drug product manufacturing across eight sites, giving Dundalk access to established quality, engineering and regulatory expertise built up over MSD's nearly two decades of manufacturing investment in Carlow, Cork and Meath, rather than having to build every capability from scratch on a standalone basis.
Dundalk's operational team takes shape
By June 2026, MSD was recruiting an Operations Director for Drug Product and Drug Substance at Dundalk, a role explicitly framed as leading 'the journey to commercialisation of a state-of-the-art vaccine manufacturing facility' and driving technology transfer, operational readiness and cultural change across the site's growing workforce.
A Senior EHS Specialist role advertised in September 2026 described Dundalk as 'a growing operational site' and set out responsibilities spanning environmental permitting, biosafety and industrial hygiene, further evidence that MSD is building out the full range of site functions, not just production roles, as Dundalk works towards full commercial vaccine output.
MSD's own careers material continues to describe Dundalk as 'the latest addition to the Ireland manufacturing network', sitting alongside longer-established sites such as Ballydine, which has supplied active ingredients for MSD medicines since 1976, and Brinny in Cork, which has specialised in vaccines and immuno-oncology testing for more than 35 years, giving the newer Louth site an established network of sister facilities to draw expertise from as it scales up.
Taken together, the pace of senior hiring at Dundalk through 2026, well beyond the initial handover from WuXi, suggests MSD is treating the site as a genuine long-term addition to its network rather than a one-off acquisition, with the leadership team now in place to carry the plant from qualification through to steady commercial vaccine supply.
The Bottom Line
MSD's investment in Ireland has been building for years, from the original Carlow vaccines plant through to 2023's €1 billion Carlow and Dunboyne expansion, and it picked up further pace in 2025 with the €500 million Dundalk acquisition and a target of around 1,000 new jobs across the network. For Carlow and the wider south-east, that steady, sustained growth, rather than any single headline announcement, is the real story of MSD's commitment to Ireland.
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