WASHINGTON (BLOOMBERG) - With a new president in the White House, the US is re-engaging with the rest of the world to combat Covid-19.
But for now, the Biden administration may hold back the one thing poorer countries desperately need: vaccines.
One day after Mr Joe Biden's inauguration last week, his chief medical adviser, Dr Anthony Fauci, pledged support for the World Health Organisation, including participation in the Covax programme to deploy vaccines globally.
Even with the US playing an active role, tough challenges remain in the effort to aid low- and middle-income nations.
The US has long been the WHO's leading partner in battling diseases, including smallpox, polio and Ebola.
And the superpower could still have a big impact in the bid to slow Covid-19 and tackle other threats after former president Donald Trump's pull-back.
Dr Lawrence Gostin, a global health law professor at Georgetown University, said he believes it's imperative for wealthy countries to start sharing vaccines before it's too late.
But doing so, he said, presents a challenge as the virus continues to spread in the US.
"When the US is in an emergency, we start looking inward," Dr Gostin said in an interview.
"Even if the rest of the world is on fire, we start looking inward."
The administration plans to fulfil US financial obligations to the WHO and looks forward to working with Covax and its partners to maximise the programme's efforts, according to a White House official who spoke on condition of anonymity.
US support may "not necessarily" include vaccines, Dr Fauci told reporters on Thursday (Jan 21) at the White House.
Helping others isn't just a moral imperative. Containing the spread of the virus in other countries could help limit mutations that might make vaccines less effective.
Meanwhile, US rivals for global influence, China and Russia, are busy offering their own vaccines in the developing world, winning friends and influence with traditional American allies.
As the pandemic extends into a second year and more contagious variants of the virus emerge, governments worldwide - though mainly wealthy ones - are rolling out vaccines to protect their populations.
That's triggered concern that by prioritising their own interests, they're ignoring the needs of less-fortunate countries while allowing the pathogen to advance.
Vaccine advocates have urged wealthy nations to share some of the supplies they've snapped up in recent months and to follow the lead of Norway, which pledged to donate extra doses through Covax.
While that may be a tough call, major economies could move in that direction when vaccines begin to curb severe illnesses and deaths at home, said Dr David Heymann, a professor at the London School of Hygiene and Tropical Medicine and former WHO official.
"It's going to be very difficult for all countries with money and pre-purchased supplies to provide that to Covax and to countries that need it at this time," Dr Heymann said.
"Once the political leaders who have made these promises to their countries do see an impact from the vaccines, they may be able to reconsider national allocations and contribute more to Covax."
As of Jan 18, vaccines had been administered in at least 49 higher-income countries, compared with just one of the world's lowest-income countries, according to Dr Tedros Adhanom Ghebreyesus, the WHO director-general.
But as Western countries have corralled supplies to protect their own populations, others are seeking to fill the void.
Russia, for instance, has signed deals with a number of low- and middle-income countries for the Sputnik V vaccine that was approved last year.
China too has extended vaccine financing and supplies to a number of countries.
Meanwhile, the US spent billions of dollars to develop and secure for its own use more than one billion doses from manufacturers, including Moderna, AstraZeneca, and the Pfizer Inc-BioNTech partnership.
Yet only 20 million doses have been administered, according to Bloomberg's tracker, covering about 6 per cent of the population.
That leaves a huge part of the US still vulnerable to Covid-19, and increases the chance that the next three months of the pandemic, and the start of Mr Biden's term, could be the worst, said Dr Michael Osterholm, director of the University of Minnesota's Centre for Infectious Disease Research and Policy.
Even so, he said, the US should also be more involved in the global programme for both diplomatic and public-health reasons.
"We want to reduce the burden on the entire world because it will help ourselves," said Dr Osterholm, who has been advising Mr Biden on Covid.
"Assisting the world is a diplomatic activity and a strategic activity."
The question is how. Mr Biden is already restoring channels of funding and personnel that the previous administration withdrew, or threatened to withdraw.
At the same time, the US has earmarked more than US$4 billion (S$5.31 billion) in additional funding for Gavi, the Vaccine Alliance, a Covax partner that distributes immunisations to children in low-income nations.
Many countries are now counting on Covax.
The programme, led by the WHO, Gavi and the Coalition for Epidemic Preparedness Innovations, said it is on track to deliver at least two billion doses - about two-thirds of which will go to lower-income economies - and to vaccinate at least a fifth of each participating country's population by the year's end.
Yet several leaders have questioned whether the programme will get the vaccines it needs as governments prioritise their own supply deals through direct talks with manufacturers, the head of the WHO said last week.
This is driving up prices and may lead to hoarding, chaos and social and economic disruption, he warned.
Even if the US can't donate doses immediately, it could help ensure that Covax is fully funded, Dr Gostin said.
To achieve that goal, Covax estimates it needs to raise an added US$2.8 billion this year.
Perhaps one of the most important contributions the US could make would be in the form of high-level diplomacy, said Dr Stephen Morrison, director of the Centre for Strategic and International Studies' Global Health Policy Centre.
The country was absent from a virtual global fund-raising event supported by the European Union in May that secured pledges of about US$8 billion.
The US, which will soon hold the presidency of the United Nations Security Council, could facilitate a meeting of global leaders to coordinate efforts against a threat to the entire world, Dr Morrison said.
Key issues to discuss could include more financing of vaccine purchases, use of vaccine surpluses, debt relief and emergency humanitarian relief.
"I think it's inevitable that there will be some kind of summitry dedicated to these issues," he said.
"US leadership has been the missing element and now it's essential."
The Biden administration could be of help in the roll-out of immunisations worldwide by pushing manufacturers to provide vaccines at affordable costs, said Professor Robert Yates, executive director of the Centre for Universal Health at Chatham House, a London-based think tank.
Just days after Mr Biden took office, Pfizer and BioNTech agreed to provide as many as 40 million vaccine doses to Covax after months of talks.
Whatever form US involvement takes, its re-emergence as partners and its highly regarded Centres for Disease Control and Prevention will strengthen the global effort and is a "good sign" for everyone, according to Dr Heymann, a former CDC employee.
"It's what America really wants," he said.
"It's been a terrible time to see the US ignore the CDC and, in general, the global health community."