A global coalition of more than 350 trade unions is renewing calls for politicians to waive the patents on Covid vaccines.
They say that failing to do so would compound supply chain crises and inflict "economic self-harm".
It comes as the World Trade Organization (WTO) tries to broker a compromise at a meeting in Geneva.
Critics argue that accelerating the rollout of vaccines is more complex than just the waiving of patents.
The dilemma being discussed at the WTO meeting centres on finding the best way to ensure the most widespread and equitable way of vaccinating the whole world from coronavirus and ending the pandemic. Successfully doing so would allow the removal of restrictions that have impaired economic growth.
Last week, the International Monetary Fund (IMF) warned that there could be a $5.3tn (£3.9tn) cost to the global economy over the next five years, if the world fails to close the massive gap in vaccination rates between advanced economies and poorer nations.
India and South Africa's governments have led calls from developing economies to relax the rules governing intellectual property of vaccines and other tools used to tackle the pandemic, such as testing equipment.
They believe doing so would accelerate vaccine rollout. The UK, Germany, Switzerland, and the European Union are amongst those who are opposed to a waiver.
The coalition of trade unions is being led by the International Transport Workers' Federation (ITF).
"These politicians seem hell bent on socio-economic self-harm to further line the pockets of Pfizer, Moderna and BioNTech billionaires," says the ITWF's general secretary Stephen Cotton.
"It is utter madness - these leaders are holding the recovery of the rest of the world to ransom."
Supply chain threat
The coalition is concerned that many of the 11 million workers they represent across 113 countries don't have sufficient access to vaccines. They warn that the global transport system faces the imminent threat of collapse if not enough workers are vaccinated.
"The inequality in access to vaccines and treatments globally is an existential threat to transport workers' personal safety, but also to the resilience of supply chains, and reinvigoration of the global economy," Mr Cotton says.
One reason supply chains are vulnerable is that only 31% of the world's 1.4 million seafarers have been vaccinated.
They play a crucial role in global trade, given that 90% of goods are carried by sea. Without vaccinations, they continue to struggle with restrictions.
This means that more than 100,000 cargo vessel staff remain at sea beyond the duration of their contracts. An estimated 14,000 people have been stuck for over 11 months, according to the Global Maritime Forum.
Developing economies such as the Philippines, Indonesia, India and Ukraine are some of the biggest contributors to the global population of seafarers. Their relatively low levels of vaccine rollout explain why the group would particularly benefit from a waiver of intellectual property rules.
However, pharmaceutical giants contend that accelerating the rollout is not as simple as waiving those rules. Beyond the formula to make the actual vaccine, expanding production means having skills, knowledge and raw materials.
"Extraordinarily complex" process
Pfizer, which worked with BioNTech to develop its vaccine, says that because it requires a biological process, vaccine production "is extraordinarily complex", requiring 280 different materials or components from 19 different countries.
In an open letter earlier this year, Pfizer's chief executive Albert Bourla wrote that the biggest restriction on expanding manufacturing was "scarcity of highly specialised raw materials" - something it has been working hard to tackle. The company says it is continuing to ramp up vaccine production.
This week rival Moderna's chairman Noubar Afeyan told Associated Press that many requests to share its technology assumed it would struggle to expand capacity, "but in fact we know we can".
Both companies say they have made considerable efforts to get their vaccines to poorer countries, as well as richer ones.
Moderna has spent $2.5bn and 10 years developing the technology behind its vaccine whilst Pfizer spent $2bn before it knew it would be successful.
It's this kind of investment that the European Union believes is encouraged when intellectual property is protected, and is why it has opposed a waiver.
A European Commission spokesperson told the BBC: "Our goal is to find a pragmatic solution to support the widest and fastest distribution of Covid vaccines that the world urgently needs.
It is, they say, trying to work with WTO partners "to enhance access to Covid vaccines and therapeutics".
Political divide remains
One solution could be compulsory licensing of private firms' technology, which is when governments force them to share it within certain conditions.
The UK government says it is "playing a leading role in the global effort to create and distribute Covid vaccines" and "will carefully review any proposal submitted" at the WTO.
However, any agreement at the WTO requires the agreement of all 164 members and many have yet to reveal which side of the argument they sit on.
The US is often influential in Geneva as the world's biggest economy. President Biden's administration supports a waiver and believes negotiations are at a critical juncture but fears that the real compromises it thinks are needed at the meeting won't be reached.
A US Trade Representative spokesperson told the BBC: "The US is doing everything in our power to ensure that everyone, both at home and around the world, has access to vaccines because more vaccinations are how we end this pandemic."
They added that their efforts at the WTO are just one part of a "comprehensive effort" to help the developing world.
Trade officials say there are encouraging signs of progress from the talks but that time is running out to reach an agreement, ahead of the WTO's ministerial conference at the end of November.