The Trump administration will pay Pfizer nearly $2bn for a December delivery of 100m doses of a Covid-19 vaccine the pharmaceutical company is developing, the health and human services (HHS) secretary, Alex Azar, announced on Wednesday. There is no approved vaccine for Covid-19, but the government has provided financial support for five vaccine candidates. The agreement is part of a plan to ramp up manufacturing in the event a vaccine is approved. The US could buy another 500m doses under the agreement, Azar said. “Now those would, of course, have to be safe and effective” and approved by the US Food and Drug Administration (FDA), Azar said during an appearance on Fox News. The vaccine candidate is being developed jointly by Pfizer and BioNTech SE, and is still in early clinical trials. The agreement is part of Donald Trump’s Operation Warp Speed vaccine program, under which multiple Covid-19 vaccines are being developed simultaneously. The program aims to deliver 300m doses of a safe and effective Covid-19 vaccine by January 2021. Under the initiative, the government will speed development and buy vaccines –before they are deemed safe and effective – so that the medication can be in hand and quickly distributed if the FDA approves or authorizes its emergency use after clinical trials. Pfizer and BioNTech said the US will pay $1.95bn upon receipt of the first 100m doses it produces, following FDA authorization or approval. Americans would receive the vaccine free, the companies said. Nearly two dozen vaccines are in various stages of human testing around the world, with several entering the final stages of clinical trials to test whether they are safe and effective. The president said at a briefing on Tuesday that “the vaccines are coming, and they’re coming a lot sooner than anyone thought possible, by years”. However, there is no guarantee a vaccine will be approved, let alone on the rapid timeline the administration would prefer. A vaccine created by the National Institutes of Health and Moderna Inc is set to begin recruiting volunteers for final-stage testing. The trial will study the safety and effectiveness of the vaccine in 30,000 people. A few other vaccines have begun smaller late-stage studies in other countries, and in the US a series of huge studies are planned to begin each month through fall in hopes of, eventually, having more than one vaccine approved. Pfizer is finishing an earlier stage of testing to determine which of four possible candidates to study in a larger, final study. Other countries are also scrambling to approve a vaccine for Covid-19. The disease has killed more than 617,000 people worldwide, according to Johns Hopkins University. Nearly 4 million Americans have been infected by the coronavirus and at least 142,000 have died. Britain announced on Monday it secured access to another 90m experimental Covid-19 vaccines made by Pfizer and others. Some campaigners have warned such moves could worsen a global scramble by rich countries to hoard the world’s limited supply of Covid-19 vaccines. China, where the coronavirus originated, also has several vaccine candidates entering final testing.