I'm sorry but you are off beam. You will be aware of the economics of marginal costing. Adding extra vaccinations will not add capital cost and will add minimal variable costs.
I made no mention of NHS pricing system which is an entirely different cost accounting animal of which I have some knowledge. You don't need to always insert a 'put down' statement!
Surely the vaccination is the capital cost, i.e. it will (almost) be a fixed price product. 10 vaccines will be £10, maybe less a discount for multiple units but still a multiple of the capital cost per unit.
The variable, controlled, cost is the number of staff on any give session.
You're the expert but product, bar discount, has always been a capital cost.