German biotech BioNTech and US drugmaker Pfizer Inc said on Monday they would begin a pivotal global study to evaluate their lead Covid-19 vaccine candidate.

If the study is successful, the companies could submit the vaccine for regulatory approval as early as October, putting them on track to supply up to 100 million doses by the end of 2020 and 1.3 billion by the end of 2021.

Patients are each given two doses of the drugmakers' vaccine to help boost immunity, so the first 100 million doses would vaccinate around 50 million people.

The study is expected to include about 120 sites globally and could include up to 30,000 participants. It will include regions heavily impacted by Covid-19.

"The initiation of the Phase 2/3 trial is a major step forward in our progress toward providing a potential vaccine to help fight the ongoing Covid-19 pandemic," said Kathrin Jansen, head of vaccine research and development at Pfizer.

The trial hones in on Pfizer's most promising vaccine candidate, which it calls BNT162b2. Earlier studies filtered out other potential vaccines.

Oxford University and AstraZeneca’s experimental vaccine has entered the final stage of clinical trials.

Pfizer already has an agreement to sell 100 million doses of its vaccine to the US government and give it the option to buy 500 million more. It is in talks with other governments, including the European Union, about similar deals.

Over 150 vaccines are being developed against Covid-19, which has claimed nearly 650,000 lives globally and crippled economies.

The vaccine utilizes chemical messenger RNA to mimic the surface of the coronavirus and teach the immune system to recognize and neutralize it. Although the technology has been around for years, there has never been an approved messenger RNA (mRNA)vaccine.

Moderna Inc and Pfizer Inc launched two 30,000-subject trials of Covid-19 vaccines that could clear the way for regulatory approval and widespread use by the end of this year, the companies said on Monday.

The trials, both announced on Monday, are the first late-stage studies supported by the Trump administration's effort to speed development of measures against the novel coronavirus, adding to hope that an effective vaccine will help end the pandemic.

Moderna stock rose 9%. Pfizer shares rose 1.6% in afterhours trade and its partner BioNTech, which developed the vaccine, rose 4.2%.

Both vaccine candidates rely on a new technology that allows for faster development and manufacturing than traditional vaccine production methods but does not have an extensive track record.