Who will make coronavirus vaccines for the developing world? India holds the key.

One prominent vaccine candidate is "a joke" that will not work for the developing world. Anyone who declares how long a vaccine will confer immunity is talking "nonsense." The world's entire population will not be immunized until 2024, he says, contrary to rosier predictions.

Poonawalla is equally frank about the gamble his company, Serum Institute of India, is making in the pandemic. He is putting $250 million of his family's fortune into a bid to ramp up manufacturing capacity to 1 billion doses through 2021.

"I decided to go all out," said Poonawalla, 39. Among the initial skeptics: his father, Cyrus, the company's founder. "He said: 'Look, it's your money. If you want to blow it up, fine.' "

It is a bet with global repercussions. In the quest for effective coronavirus vaccines, India is poised to play a critical role in supplying the developing world, which is starting the race with a distinct disadvantage.

Wealthy countries have already grabbed a major chunk of the available supply. The United States, the United Kingdom, Japan and Canada have struck deals large enough to vaccinate their entire populations. By contrast, a pooled global effort to distribute vaccines equitably to more than 150 countries - including dozens of low-income nations - has secured only 700 million doses.

Pfizer, which announced stellar early results for its vaccine candidate Monday, has not struck any deals to supply its product to developing countries, according to an analysis of publicly available data by Airfinity, a research firm in the United Kingdom. Pfizer's vaccine must also be stored at ultra-cold temperatures, a major challenge in much of the world.

Rich nations are "all cutting in line and hoarding vaccine supply to immunize as many people as possible, even if this leaves other countries unable to immunize those at highest risk," said Nicholas Lusiani, a senior adviser at Oxfam America, a nonprofit group devoted to fighting poverty.

Enter Indian vaccine makers, led by Serum Institute, the largest manufacturer in the world by volume. Well before the pandemic, India was a "vaccine powerhouse" specializing in affordable exports to low- and middle-income countries, said Andrea Taylor, an assistant director at the Duke Global Health Innovation Center.

Taylor said countries such as Brazil and China also have manufacturing capacity, but she singled out Indian vaccine makers because they moved so quickly to form tie-ups with global companies and increase their own production. India is "going to be the absolute star in the story," she said.

Anthony Fauci, the top infectious-disease specialist in the United States, shared that sentiment during a panel earlier this year. India's manufacturing capability is "going to be very, very important" as effective vaccines emerge, he said.

Four major pharmaceutical companies - AstraZeneca, Novavax, Johnson & Johnson and Sanofi - have reached agreements to produce at least 3 billion vaccine doses for low- and middle-income countries, Airfinity's research shows. Serum Institute is set to manufacture more than two-thirds of those doses.

Some of the agreed-upon supply to low- and middle-income countries will come through the pooled initiative backed by the World Health Organization, known as the Covid-19 Vaccines Global Access Facility, or Covax. Covax includes higher- and lower-income countries, more than 150 in total. The United States declined to join.

Covax is being co-led by Gavi, a nonprofit vaccine alliance. In September, Gavi announced a partnership with the Bill and Melinda Gates Foundation to pay Serum Institute in advance for 200 million vaccine doses, at a cost of $3 each, to be distributed in developing countries, hopefully in early 2021. The $600 million infusion will help Serum ramp up production.

Gavi and the Gates Foundation "want to assure vaccine supply at an affordable price," said Poonawalla, Serum's chief executive. His aim, meanwhile, is to cover some of his costs. "At least my risk is taken away so I can sleep at night," he said.

The partnership with Serum, given its size, is "crucial" to Gavi's larger goal of ensuring that no country is left behind in the quest for vaccines, said Dominic Hein, who works on Gavi's efforts to make vaccines more readily available in low-income countries.

Under the agreement, more than 60 countries - largely in Africa and Asia - would receive the vaccine developed by Oxford University and AstraZeneca or the vaccine under development by Novavax.

Serum Institute has struck deals to manufacture both vaccines, which are in Phase 3 trials. It has also inked deals to make two other vaccines, developed by the American biotechnology company Codagenix and Britain's SpyBiotech, and is working on its own vaccine candidate that it hopes will enter trials late next year. While the Indian company has reached manufacturing agreements with American companies such as Novavax and Codagenix, it is not currently exporting its vaccines to the United States.

India has recorded the second-highest number of coronavirus cases in the world - more than 8.5 million. Those numbers mean India is a crucial market for future vaccines and an effective place to test them.

Advanced clinical trials of three vaccine candidates are underway in India: the AstraZeneca vaccine and vaccines developed by two Indian pharmaceutical companies, Zydus Cadila and Bharat Biotech. An Indian company is also starting clinical trials of Russia's vaccine candidate, Sputnik V.

"Whether India makes a vaccine by itself or not, from a manufacturing standpoint, it's going to be playing a very, very important role," said Mahima Datla, managing director of Biological E., a 67-year-old vaccine producer based in the city of Hyderabad. Datla also sits on the board of Gavi.

India's health minister recently predicted that the country would be in a position to start distributing a vaccine within the next six months. The government is working on a plan to immunize as many as 250 million people by July, he said.

Reaching that goal will require the manufacturing heft of Serum Institute. The company has diverted capacity from existing vaccines and started work on a new production facility to be completed next year at its headquarters in the western Indian city of Pune.

Poonawalla said the company has pledged to keep half of the vaccines it makes for use within India. It has already begun manufacturing the AstraZeneca vaccine, he said. About 20 million doses have been made, and he expects to have 10 times that amount ready in the next four months.

He is optimistic that in 2021, a new coronavirus vaccine will be licensed for public use every couple of months. "That's the good news," Poonawalla said. The less-good news is that it remains unclear which vaccine, if any, will offer long-term protection from the virus. "Nobody wants a vaccine that is only going to protect you for a few months," he said.