AstraZeneca has doubled the manufacturing capacity for its potential Covid-19 vaccine to 2bn doses after striking a number of deals that include two health organisations backed by Bill and Melinda Gates.

Last month the pharmaceutical giant said it could manufacture 1bn doses of the vaccine that it is developing in partnership with with researchers at Oxford University.

On Thursday, AstraZeneca announced that it had signed an agreement with the Serum Institute of India to produce 1bn doses aimed at low and middle income countries. It plans to provide 400m doses before the end of 2020.

AstraZeneca also struck a deal worth $750m (£595m) with two health organisations backed by Microsoft co-founder Bill Gates and his wife Melinda. Those organisations, Coalition for Epidemic Preparedness Innovations (CEPI) and Gavi vaccines alliance, will help find manufacturing facilities to produce and distribute 300m doses of the vaccine, with delivery set to start by the end of the year.

The new deals are aimed at guaranteeing early supply of the vaccine to lower income countries. It is as yet unclear if vaccines will work against Covid-19 but dozens of companies are in the race to develop one.

AstraZeneca, which last month overtook Royal Dutch Shell to become the UK’s largest company by market value, said the latest agreements were part of efforts to buildsupply chains for the potential vaccine at no profit. The company has already agreed to supply 300 million doses of the potential vaccine to the US and a further 100m to the UK, with the first deliveries expected in September.

“Our goal is not to leave anybody behind, and we’ll keep working very hard … to make sure this vaccine is rapidly and widely available across the world,” said Pascal Soriot, the chief executive of AstraZeneca.

Richard Hatchett, chief executive of CEPI, said the World Health Organization will take charge of developing a “recommended allocation schemes” so that the vaccines produced through the new partnerships are initially distributed to the people who need it most.

That could include healthcare workers and vulnerable people who are most at risk from Covid-19, including the elderly and people with underlying health conditions like hypertension or diabetes, Hatchett explained. He assured the allocation process would be “open and inclusive and transparent as WHO processes are.”

Soriot said AstraZeneca was in talks with “additional parties that could be interested” in the 300 million spare doses that have yet to be called for.

The vaccine, known as AZD1222, is currently in trials involving about 10,000 adult volunteers. Soriot said he expects to know whether the vaccine works when those trials come to a close in August.

After that, vaccines could start being distributed as early as September.

Hatchett said the search for a vaccine against Covid-19 was “absolutely the most pressing challenge of our time.”

However, he admitted that the organisation was taking a “substantial risk” by investing in manufacturing while trials were still ongoing, and admitted there was a possibility that the vaccine may not work.

However, if that ends up being the case, CEPI could offer to help other vaccine manufacturers that use similar production methods. “That is one way of managing the risk and tolerating the very large financial risk of beginning manufacturing up front,” Hatchett said.

“Obviously if the vaccine is successful, placing that early bet on the manufacturing gives a huge payout, because you end up with tens or even hundreds of millions of doses that become available at the earliest possible moment that your’e sure the vaccine is safe and effective,” Hatchett added.

CEPI was previously working with the University of Oxford to try to develop a vaccine for Middle East respiratory syndrome (Mers), which is another form of coronavirus.

“As far as the chance of the [Covid-19] vaccine working, I would say we all have pretty good hope from what we’ve seen so far, but we can’t be sure of course,” Soriot said.

The pharmaceuticals boss said the company would consider further partnerships that could ramp up capacity even further, but said authorities should hedge their bets.

“It would probably make sense for society to bet on two or three different technologies, not only our vaccine. So you’d expect other vaccines to be made available,” he said.

“We’ll certainly look at additional capacity, but at 2bn [doses] … you’d already be making a big impact,” Soriot added.