Seafarers, truck drivers and airline workers have endured quarantines, travel restrictions and complex Covid-19 vaccination and testing requirements to keep stretched supply chains moving during the pandemic.

But many are now reaching their breaking point, posing yet another threat to the badly tangled network of ports, container vessels and trucking companies that moves goods around the world. In an open letter Wednesday to heads of state attending the United Nations General Assembly, the International Chamber of Shipping (ICS) and other industry groups warned of a “global transport system collapse” if governments do not restore freedom of movement to transport workers and give them priority to receive vaccines recognized by the World Health Organization.

“Global supply chains are beginning to buckle as two years’ worth of strain on transport workers take their toll,” the groups wrote. The letter has also been signed by the International Air Transport Association (IATA), the International Road Transport Union (IRU) and the International Transport Workers’ Federation (ITF). Together they represent 65 million transport workers globally. “All transport sectors are also seeing a shortage of workers, and expect more to leave as a result of the poor treatment millions have faced during the pandemic, putting the supply chain under greater threat,” it added.

Guy Platten, secretary general of the ICS, said that worker shortages are likely to worsen towards the end of the year because seafarers may not want to commit to new contracts and risk not making it home for Christmas given port shutdowns and constant changes to travel restrictions.

That will heap pressure on stretched supply chains and could, for example, worsen current challenges with food and fuel supply in the United Kingdom. “The global supply chain is very fragile and depends as much on a seafarer [from the Philippines] as it does on a truck driver to deliver goods,” added Stephen Cotton, ITF secretary general. “The time has come for heads of government to respond to these workers’ needs.”When Karynn Marchal and her crew were told that they wouldn’t be allowed to go on shore upon docking in Hokkaido, Japan it was a big hit to morale.