Wealthy countries have already locked up more than a billion doses of coronavirus vaccines, raising worries that the rest of the world will be at the back of the queue in the global effort to defeat the pathogen.
Moves by the US and the UK to secure supplies from Sanofi and partner GlaxoSmithKline, and another pact between Japan and Pfizer, are the latest in a string of agreements.
The EU has also been aggressive in obtaining shots, well before anyone knows whether they will work.
Although international groups and a number of nations are promising to make vaccines affordable and accessible to all, doses will likely struggle to keep up with demand in a world of roughly 7.8bn people.
The possibility that wealthier countries will monopolise supply, a scenario that played out in the 2009 swine flu pandemic, has fuelled concerns among poor nations and health advocates.
The US, Britain, EU, and Japan have so far secured about 1.3bn doses of potential Covid immunisations, according to London-based analytics firm Airfinity.
Options to snap up more supplies or pending deals would add about 1.5bn doses to that total, its figures show.
“Even if you have an optimistic assessment of the scientific progress, there’s still not enough vaccines for the world,” according to Rasmus Bech Hansen, Airfinity’s chief executive officer.
"What’s also important to consider is that most of the vaccines may require two doses," he said.
A few frontrunners, such as the University of Oxford and partner AstraZeneca and a Pfizer-BioNTech collaboration, are already in final-stage studies, fuelling hopes that a weapon to fight Covid will be available soon.
But developers must still clear a number of hurdles, and worldwide supply may not reach 1bn doses until the first quarter of 2022, Airfinity forecasts.
Investing in production capacity all over the world is seen as one of the keys to solving the dilemma, and pharma companies are starting to outline plans to deploy shots widely.
The World Health Organization, the Coalition for Epidemic Preparedness Innovations, and Gavi, the Vaccine Alliance are working together to bring about equitable and broad access. They outlined an $18bn (€15.25bn) plan in June to roll out shots and secure 2bn doses by the end of 2021.
The initiative, known as Covax, aims to give governments an opportunity to hedge the risk of backing unsuccessful candidates and give other nations with limited finances access to shots that would be otherwise unaffordable.
Countries would need to strike a series of different agreements with vaccine makers to raise their chances of getting supplies, as some shots will not succeed — a situation that could lead to bidding battles and inefficiencies, Seth Berkley, Gavi’s CEO, said in an interview.
“The thing we worry about most is getting a tangle of deals,” he said. Some 78 nations have expressed interest in joining Covax, he said.
In addition, more than 90 low- and middle-income countries and economies will be able to access Covid vaccines through a Gavi-led programme, the group said.
AstraZeneca in June became the first manufacturer to sign up to Gavi’s programme, committing 300m doses, and Pfizer and BioNTech signalled interest in potentially supplying Covax.
Brazil, the nation with the second-highest number of coronavirus cases, also reached an agreement to secure doses of the Oxford vaccine with AstraZeneca.