Covid-19 vaccines could roll out in the UK in the first half of next year, with the NHS preparing to give doses "when they are available" by Christmas.
After successful studies, vaccines could be introduced in general practitioners' practices, pharmacies and mass test centers.
But health chiefs say a mass vaccination program is unlikely to begin until next year.
More than 200 candidates for coronavirus vaccines are currently being tested worldwide.
Here is everything you need to know about racing for a Covid-19 vaccine.
What progress is being made with Covid-19 vaccines?
A total of 44 of the vaccine candidates under development are in the clinical trial stage.
Of these, nine are in the third phase of clinical evaluation and will be administered to thousands of people for confirmation of safety and effectiveness.
There are two front runners in the Covid-19 vaccine race – one from German biotech company BioNtech and US pharmaceutical company Pfizer, and another being developed by the University of Oxford and AstraZeneca.
Both vaccines are currently in phase three of clinical trials.
The Oxford vaccine called ChAdOx1 nCoV-19 uses a weakened version of a cold virus (adenovirus) that causes infections in chimpanzees.
Other potential vaccines in phase 3 trials are those from US drug maker Moderna and biotech company Novavax.
What studies are going on in the UK?
In addition to the Oxford vaccine, Imperial College London is developing a coronavirus sting.
The Imperial vaccine is in its first phase of clinical trials, where doses are given to a small group of people to see if it is safe and to learn more about the immune response it elicits.
The pharmaceutical companies Sanofi and GlaxoSmithKline have also teamed up to provide a Covid-19 vaccine by the middle of next year.
The Sanofi / GSK candidate is in the second phase, with the vaccine being given to hundreds of people so that scientists can learn more about its safety and the correct dosage.
They plan to start the phase 3 study by the end of the year.
When will the results of these studies be available?
UK Vaccine Task Force leader Kate Bingham said data from vaccine trials at the University of Oxford and AstraZeneca, as well as Pfizer with BioNTech, may be available this year.
She said if she put up "pink specs" she would hope to see positive interim data from Oxford and Pfizer BioNtech in early December.
Oxford vaccine team leader Professor Andrew Pollard said he was optimistic that data on the vaccine's safety and effectiveness will be available by the end of the year.
Professor Robin Shattock, who leads Imperial College London's Covid-19 vaccine effort, said data on its effectiveness will be available by mid-next year.
Does the UK have access to these potential vaccines?
In August, the government announced that the UK had secured access to six Covid-19 vaccine candidates in development, equivalent to 340 million doses.
Ms. Bingham said around four million doses of vaccine should be available by the end of the year.
The UK has also received 30 million doses of the vaccine developed by BioNtech and Pfizer.
Offerings include four different types of vaccines – adenoviral vaccines, mRNA vaccines, inactivated whole virus vaccines, and protein adjuvant vaccines.
Adenoviral vaccines are weakened versions of adenoviruses, while mRNA candidates consist of small or inactivated doses of the entire disease-causing organism.
Inactivated whole virus vaccines, on the other hand, contain whole bacteria or viruses that have been killed, while protein-adjuvant bursts are those where an adjuvant is added to boost the immune response.
Should any of these candidates be admitted, the most vulnerable, the elderly, those living in nursing homes, and health and social care workers will stand in line to receive a bump, followed by those at high risk.
When will a coronavirus vaccine be available?
A vaccine typically takes years, often decades, to develop, but scientists working on potential coronavirus bumps hope to get the same amount of work in a few months.
Most experts are optimistic that a vaccine is expected to be available in mid-2021, around 12 to 18 months after the new coronavirus first appeared.
Sir Simon Stevens, CEO of NHS England, said the "expectation" is that every vaccination program will begin in the new year – until positive results from clinical trials are available.
Meanwhile, Ms. Bingham said she has 50% confidence that by Easter or early summer next year all vulnerable people in the country will have a vaccine.
Prof. Pollard said clinical trials must take place in the child population before Covid-19 vaccines can be given to adolescents.
He said, “These studies are in the pipeline, but right now we don't have any data on immune response or child safety, and that has to be done in the normal scientific process, and I would anticipate that it will be late this year or early next year happen. & # 39;
Where are the vaccines given?
Sir Simon said a potential vaccination program will have vaccines delivered to general practitioners' offices, pharmacies and mass test centers – including the Nightingale hospitals.
He said general practitioners will be on standby from December in case a vaccine is made available before Christmas.
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