Kate Bingham, head of the UK's Vaccine Taskforce, has already warned there is only a 'slim' chance scientists will have a jab before Christmas.
Bingham today warned, in the Lancet, that the first generation of vaccines, which are all still in human trials — are 'likely to be imperfect'.
Ms Bingham went on to say: 'We should be prepared they might not prevent infection but rather reduce symptoms, and, even then, might not work for everyone or for long.'
She added 'we do not know that we will ever have a vaccine at all', cautioning that 'many, and possibly all' of the vaccines currently being investigated could fail.
Ms Bingham wrote: 'A major challenge is that the global manufacturing capacity for vaccines is vastly inadequate for the billions of doses that are needed, and the UK manufacturing capability to date has been equally scarce.
'There will not be one successful vaccine, or one single country, that is able to supply the world.
'We urgently need international cooperation to pool risks and costs, address barriers to access, and scale up the manufacturing capacity to produce sufficient doses to protect everyone at risk of SARS-CoV-2 infection globally.'
She went on to reveal that there are 'deployment plans' for when a Covid-19 vaccine is ready because there will be huge logistical challenges in roll-out. These have been made for the NHS, GP surgeries, pharmacies, care home and pop-up sites.
Earlier this month Ms Bingham confirmed that not everyone - potentially only half - of the British population would be vaccinated if a jab was proven effective against the coronavirus.
Lastly she said only vaccines that have the potential for approval by regulators and delivery as early as the end of 2020 or, at the latest, in the second half of 2021, have been considered.
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