More than 91 million people in the US have received at least one dose of a vaccine, with 32 million of those already fully vaccinated.

The country is administering an average of two million shots a day with President Joe Biden aiming to vaccinate the adult population of 270 million by the end of May.

The rapid progress of the rollout has boosted Hirshland’s hopes of sending a US delegation to Tokyo 2020 that would have received both doses of a vaccine.

"We are more optimistic than ever in hoping Team USA athletes will be readily and easily vaccinated well before the Games, and hopefully, some likely even before their trials," Hirshland said.

"The vaccine situation is looking very positive.

"The broad base of athletes may have access to the vaccine sooner than we thought initially possible.

"This is great news and we're feeling really positive about the progress we're seeing here in the United States, both in its advantage to US athletes as well as international athletes living and training in our country right now."

Hirshland did not rule out holding mass vaccination events to help administer doses to athletes ahead of the Games.

"It is possible that vaccines may be readily and widely available in local communities across the country as early as May based on what the administration is telling us," said Hirshland.

"That certainly provides the easiest logistical pathway for athletes training in communities across the country, but we are also exploring opportunities to help support that distribution.

"Ideally the vaccines are administered well in advance of that, but we're exploring every option. 

"We're focused on being as prepared as we can."

Under plans for Tokyo 2020, vaccination will not be mandatory for athletes to compete.

The International Olympic Committee has also claimed it will not jump the queue ahead of those who need a vaccination most, but the organisation has encouraged athletes to accept vaccines when offered as a sign of respect for the host country and its people.

Hirshland said the "vast majority" of US athletes would opt for the vaccine, but she was expecting some to decline to the jab.

"I absolutely expect there will be Team USA athletes who do not choose to take a vaccine," Hirshland said.

"We will respect that right.

"There are a variety of factors that may play into those decisions.

"Our medical teams are working with athletes on a one-on-one basis to make sure they have the information they need to make the right choice for themselves.

"With or without the vaccine, we're confident we can keep everybody healthy and safe regardless."

The US has suffered more deaths from coronavirus than any other country in the world, registering more than 500,000 fatalities since the start of the pandemic.