US President-elect Joe Biden on Friday slammed the Trump administration's distribution of Covid-19 vaccines as a "travesty," and announced a plan to speed up rollout that could delay people's second dose.
More than 365,000 people have died from the coronavirus in America, the world's hardest-hit country, including some 4,000 on Thursday alone.
"Vaccines give us hope, but the roll-out has been a travesty," Biden told reporters in Wilmington, Delaware.
He said distribution of the vaccine would be "the greatest operational challenge we will ever face as a nation."
Biden's comments came shortly after a spokesman said the new administration planned to release every available dose of Covid-19 vaccine produced in the country, rather than holding back half the supply to make sure people receive their booster shots on time.
Biden "supports releasing available doses immediately and believes the government should stop holding back vaccine supply so we can get more shots in Americans' arms now," TJ Ducklo told the media.
But it was not clear how this plan would address the problem, since the main bottleneck in the US currently is not scarcity of vaccines, but rather the slow administration of shots by providers.
Around six million Americans have so far received their first shot, even though the target for December alone had been 20 million.
But as of January 7, the federal government had overseen the distribution of more than 21 million first doses -- with around 15 million lying in freezers at hospitals and clinics across the country, awaiting use.
This has become a source of friction between federal and state authorities, with health secretary Alex Azar this week urging states to not let rigid priority lists prevent shots from reaching arms.
In New York, for example, Governor Andrew Cuomo signed an order threatening fines of up to $1 million for health care providers who violate the priority system.
As a result, clinics have been forced to throw out doses that expired, rather than giving them to people whose priority group has not yet come up, according to reports.
- Delayed boosters -
Both vaccines currently authorized in the US, developed by Pfizer and Moderna, require recipients to receive booster shots -- after three and four weeks, respectively.
Authorities in Britain and elsewhere have said that the second dose could be delayed to quickly scale up the number of people who can be reached, even if it means slightly reducing the level of individual protection in the interim period.
Saad Omer, a vaccine researcher and director of Yale's Institute for Global Health, told AFP this week that he only saw a need for such a strategy in countries where supply is the problem, which is not the case in the US.
The idea of delaying the second dose has also been opposed by the Food and Drug Administration as well as top government scientist Anthony Fauci, because it has not been rigorously studied.