(Reuters) - French drugmaker Sanofi SASY.PA has been making drug-shortage contingency plans for more than a year to prepare for Britain and the European Union failing to reach a Brexit transition deal, the Wall Street Journal reported on Tuesday, citing a source.

Stocks have been increased for all therapeutic areas by about four weeks to a total of 14 weeks’ supply, excluding medicines that are in constant shortage. The stock for vaccines, of which Sanofi is a large producer, has also been increased where possible, the WSJ report said.

Quality control, for which Sanofi sends batches of medicine back to the continent from its two plants in Britain, would no longer be possible in the case of a hard Brexit and some reductions to its 1,800 strong UK workforce would become necessary, the report said.

Sanofi’s Brexit-related preparations began about a year ago and its UK division began building up its stocks about six months after, the report added.

More than 2,600 drugs have some stage of manufacture in Britain and 45 million patient packs are supplied from the United Kingdom to other European countries each month, while another 37 million flow in the opposite direction, industry figures show.

Brexit threatens the free flow of these goods, given stringent medicine regulations that will require the retesting of drugs shipped across borders in the absence of an agreed trading arrangement.

The European Medicines Agency has warned drugmakers they needed to be ready for a possible hard Brexit in 2019 and said it had “serious concerns” about preparations in the case of 108 medicines made only in the UK.

Earlier this month, British drugmaker AstraZeneca Plc AZN.L said it was increasing stockpiles of those medicines in Britain and continental Europe that could be affected by Brexit by around 20 percent.

Sanofi did not immediately respond to a request for comment.