The US has thrown its support behind an initiative at the World Trade Organization (WTO) to waive intellectual property protections for coronavirus vaccines.
India and South Africa proposed the move, which they said would increase vaccine production around the world.
But drugs manufacturers argue it may not have the desired effect.
US Trade Representative Katherine Tai said that “extraordinary times call for extraordinary measures”.
And she warned that it would take time for WTO members to reach a consensus decision on the matter.
India and South Africa were the leading voices in a group of about 60 countries which for the last six months has been trying to get the patents on vaccines set aside.
However, they met with strong opposition from the previous US administration of Donald Trump, the UK and the EU.
But Mr Trump’s successor as US President, Joe Biden, has taken a different tack. He backed a waiver during the 2020 presidential campaign and reiterated his support on Wednesday.
The head of the World Health Organization (WHO) called the move a “monumental moment” in the fight against Covid-19.
If approved, supporters say, the waiver would allow production of vaccines to be ramped up and provide more affordable doses for less wealthy countries.
Many developing countries have argued that rules requiring countries to protect patents and other forms of intellectual property are an obstacle to ramping up the production of vaccines and other products needed to tackle the pandemic.
The US had previously helped block WTO negotiations about the waiver proposal led by India and South Africa aimed at helping developing countries to produce vaccines using the intellectual property of pharmaceutical companies.
Ms Tai said the US would now embark on negotiations at the WTO to try and secure the waiver. This could take time as WTO decisions require a consensus of all 164 members.
It is a truly extraordinary moment.
President Biden’s trade representative released a statement saying the White House would support a waiver on the intellectual property rights owned by the makers of Covid-19 vaccines during the pandemic.
The campaign for this has been going on amongst NGOs, some US Congressional Democrats and some developing countries such as India and South Africa. And as recently as March the US, the UK and the EU were resisting the moves in negotiations at the WTO in Geneva.
Katherine Tai has been seeing top pharmaceutical companies and also raised the issue with UK International Trade Secretary Liz Truss at a virtual meeting last month.
In an interview with the BBC last month, WTO chief Ngozi Okonjo-Iweala told the BBC that if vaccine manufacturers failed to supply the world, they would have to transfer the know-how.
Drugs companies are adamant that the patents are not the bottleneck here, it is manufacturing capacity. But the Indians and South Africans have disagreed, with South African President Cyril Ramaphosa decrying what he called “vaccine apartheid”, saying his country and some in South America could ramp up production.
The US move does tilt the balance of power in the WTO towards a waiver. But the position of both the UK and the European Union will now also come under careful scrutiny.
Tedros Adhanom Ghebreyesus, head of the WHO, called the US decision “historic” and marked “a monumental moment in the fight against Covid-19”.
But pharmaceutical companies have voiced their opposition, insisting that patents are not the primary obstacle, and cautioned that the move could stifle innovation.
The International Federation of Pharmaceutical Manufacturers and Associations called the move “disappointing”.
“A waiver is the simple but the wrong answer to what is a complex problem,” the Geneva-based lobby group said.
Dr Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security, told the Reuters news agency that the waiver “amounts to the expropriation of the property of the pharmaceutical companies whose innovation and financial investments made the development of Covid-19 vaccines possible in the first place”.
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