Cinical trials in adults showed a 77% reduction in the risk of developing covid after been treated with Evusheld, yet the government say they will not be buying any doses. 

There are around 500,000 people in the UK with suppressed immune systems . That means their bodies struggle to produce antibodies, so the existing vaccines offer little to no protection, leaving them very vulnerable to covid. 
Evusheld would give a layer of protection and help to avoid patients having to isolate over winter.