Covid: Will there be more than one coronavirus vaccine?
In the past two weeks, both Pfizer and BioNtech and Moderna have announced hugely successful trials of their Covid-19 vaccines.
Others are in development, while a third major trial - from Belgian company Janssen - is under way in the UK.
Why do we need a vaccine?
If you want your life to get back to normal, then we need a vaccine.
Even now, the vast majority of people are still vulnerable to coronavirus infection. It's only the restrictions on our lives that are preventing more people from dying.
But a vaccine would safely teach our bodies to fight the infection. It would either stop us catching coronavirus in the first place or at least make Covid less deadly.
Having a vaccine, alongside better treatments, is "the" exit strategy.
Which vaccines look most likely to succeed?
Pfizer/BioNtech is the first pharmaceutical company to share information from the final stages of vaccine testing.
The data suggests the jab could prevent more than 90% of people from getting Covid-19.
About 43,000 people have been given the vaccine, and no safety concerns have been raised.
Moderna ran a trial of its vaccine on 30,000 people in the US, in which half were given dummy injections,
It says its vaccine protects 94.5% of people, after only five of the first 95 trial participants who developed Covid symptoms had received the real vaccine.
Trial results are also due in the next few weeks on a vaccine being developed by British drug manufacturer AstraZeneca and scientists at the University of Oxford.
Meanwhile encouraging data on a Russian vaccine called Sputnik V has also been released.
Based on interim results from a phase 3 trial, the same stage reached by the Pfizer jab, Russian researchers report that it is 92% efficient.
What other vaccines are being developed?
More results from other teams working on advanced trials are also expected in the coming weeks and months.
The Janssen trial has started the job of recruiting 6,000 people across the UK. Other countries will join the effort to bring the total up to 30,000.
The company already has one large-scale trial of its vaccine, in which volunteers receive one dose. This work will see if two jabs give stronger and longer-lasting immunity.
Several other vaccines are in the final testing stage, including Wuhan Institute of Biological Products and Sinopharm in China, and Russia's Gamaleya Research Institute.
However, a trial in Brazil for a drug developed by the Chinese firm Sinovac has been suspended after what was described as a "severe adverse incident" - believed to be a volunteer's death.