There are around 140 vaccines currently in preclinical trials. The clinical trials are divided into 3 phases.
Tests carried out on a small number of people to see if the vaccine is safe to use in humans. There are 18 in this phase.
Tests carried out in a larger number of people to see if the vaccine triggers an immune response to the vaccine. There are 11 in this group.
Tests carried out on a much larger number , typically hundreds to thousands to see if the vaccine actually works to protect against the virus. This also includes a control group who are given placebo. There are 5 in this group. Phase 3 will probably also sort out if there is a different response in the BAME group of by blood type. This group has been seen to be susceptible to having a severe reaction to Covid, as was the case with SARS.
So when? Don’t hold your breath! Current thinking is we might have one in 6 months at best, many are suggesting 12 to 18 months is more likely. The Russian announcement of a vaccine ready to roll is at best premature since they have as yet to complete phase 2 testing let alone phase 3.
Now is not the time to lower our guard. Aberdeen was a salutary wake up call if indeed one was needed.