I would spend every penny unblocking the pathway to a vaccine.

• Multithreading stages of the clinical trials. E.g. have combination vaccine safety trials started ahead of proof of efficacy for individual trials?
• Reviewing what the target for effectiveness really is. E.g. would a vaccine which tips the population reproduction rate below 1 without providing individual level guarantees? How long would we wait to see if anything better would become available? Would we be prepared to risk needing two phases of vaccination? Would we make an earlier safe vaccine with low efficacy available optionally?
• Cohort recruitment should be easy, volunteerism is at max right now. If it is not, the problem must be logistical. What support is needed (coach services, apps etc)?
• Streamlining regulatory hurdles. Assume tests go well, is there any blocking legislation which does not make sense? What bills could we predict are necessary now to pre-empt the blockage?
• Preparing for mass production of different kinds of vaccines. Assume each system works and ask what would be needed to scale it out. Make bets on any cheap elements of any relevant systems. Use the time before production starts to duplicate existing production facilities.
• Readying the logistics for administration. E.g. given PPE shenanigans, it wouldn't surprise me if we had a lack of disposable syringes etc. Most of this could be prepared in advance of actually having a vaccine.

The basic ideas and test candidates are already known. The lag between now and mass roll out is therefore (mostly) dependent on our organizational skills.

<waving hands> UK GDP is ~£2.9 trillion. The recession will shave at least 10% off that. The government takes ~30% of GDP in tax. If bringing forward mass vaccination could shave a quarter off an 18 month recession, it would be revenue neutral to pay £100 billion to do it. So, if some of the above sounds too expensive, it's because a bigger budget is necessary and likely justified. It would take an order 1000x correction to change this reasoning. </waving hands>