Uber and Lyft are set to offer free rides to anyone travelling to or from Covid-19 vaccination sites in the US.
They will be available within the next two weeks through the taxi firms' apps until 4 July as part of government efforts to increase vaccine take-up, the White House announced on Tuesday.
It comes as demand for jabs in the US has slowed in recent weeks.
The boss of Uber said: "Vaccines are our best hope to beat this pandemic".
Chief executive Dara Khosrowshahi added: "This is a proud moment for me, for Uber, and for our country. More and more Americans continue to get vaccinated every day - let's keep moving forward, together."
President Joe Biden has said he would like to see 70% of US adults receive at least one vaccine dose in time for 4 July Independence Day celebrations.
As of Monday, 46% of Americans have received at least one vaccine dose, according to the US Centers for Disease Control and Prevention.
The new initiatives come at a time when US demand for vaccines has declined significantly, forcing the administration to figure out new ways to motivate people to get vaccinated.
The free rides from the ride-hailing apps were highlighted by the White House as part of efforts to help the vaccine roll-out.
Neither will be paid by the government to transport people to and from the sites, but said they will pick up the costs themselves.
A new feature will launch in about two weeks on both apps, which will allow customers to get a code they can use to get rides to and from a vaccination site after providing some details.
Uber and Lyft have previously announced free rides to vaccine clinics would be available to vulnerable communities lacking healthcare and transportation at increased risk of Covid-19.
But the new offer will be available to all US residents with a vaccine appointment.
Lyft said that its code would cover $15 (£10.60) each way, and it expects that would cover "most, if not all, of riders' fares".
Its co-founder and president John Zimmer said: "The vaccine is the key to getting us all moving again, and we're proud to do our part to move the country forward.
"We've always believed transportation has the power to improve people's lives, and this initiative makes that truer than ever."
An Uber spokeswoman told the BBC that more details would be announced for its app in the coming weeks.
Both transport firms also confirmed that the offer would not have an impact on drivers' take-home pay.
The partnership comes after Uber sent a letter to the Biden team in December, offering help with vaccinations.
It also urged the administration to maintain Uber drivers' status as independent contractors, while offering the ability to provide some benefits.
Mr Biden campaigned on providing more benefits to gig workers by reclassifying them as employees, which the companies involved are against.
The rides build on existing schemes Uber and Lyft launched at the end of last year, which help the public but also the companies as they seek to have drivers and riders return to the road.
Uber had offered 10 million self-funded free or discounted rides to vaccination sites, while Lyft said it would provide an uncapped amount of free vaccination rides paid for in partnership with other corporate sponsors.
Mr Biden also will announce funding through the Federal Emergency Management Agency (FEMA) for states for on-the-ground efforts to promote vaccinations, such as phone banking and door-to-door canvassing.
The announcement follows attempts by other companies to encourage customers to get vaccinated.
McDonald's announced on Tuesday that in the US it would start printing "We can do this" slogans, alongside links to websites with further information about vaccines, on its coffee cups.
Consumer giant Unilever will also be giving away milkshakes and ice creams to healthcare workers and those getting vaccinated across several US sites on 14 May.