A coronavirus vaccine being developed in the UK will provide protection against the disease "for about a year", according to the drugmaker currently carrying out trials.
AstraZeneca has joined forces with the UK government to support a COVID-19 vaccine developed by the University of Oxford.
Human trials of the vaccine are under way, with the firm already having reached agreements to supply around two billion doses across the world.
Pascal Soriot, AstraZeneca's chief executive, told Belgian radio on Tuesday that a phase one trial of the vaccine in Britain was due to end soon, while a phase three trial has already begun.
A phase three trial is usually the final phase in the clinical development of a vaccine and sees the vaccine given to thousands of people to be tested for efficacy and safety.
Commenting on the likely protection the Oxford vaccine will provide, Mr Soriot told broadcaster Bel RTL: "We think that it will protect for about a year."
He added: "If all goes well, we will have the results of the clinical trials in August/September. We are manufacturing in parallel.
"We will be ready to deliver from October if all goes well."
AstraZeneca has previously acknowledged the vaccine may not work, despite its commitments to progress its clinical programme and to scale up manufacturing.
The University of Oxford vaccine, now known as AZD1222, is based on a weakened version of the common cold that causes infections in chimpanzees.
It also contains the genetic material of the spike protein of SARS-CoV-2 - the strain of coronavirus that causes the COVID-19 illness.
After vaccination, the immune system is primed to attack COVID-19 if it later infects the body.
The UK government has also given £41m to the development of another coronavirus vaccine developed by London's Imperial College.
Human trials of the vaccine - on 300 people - will begin this week.
Unlike many traditional vaccines, the Imperial College vaccine uses synthetic strands of genetic code - known as RNA - based on the virus's genetic material.
The human trials will be the first test of a new self-amplifying RNA technology.
Kate Bingham, the chair of the UK government's vaccine taskforce, said: "Their self-amplifying technology has the potential to be a real game-changer, not only for a COVID-19 vaccine but for the development of future vaccines".