Why do you think it wouldn't be efficient for general use? Do you think it'll be expensive?
The former is a measure of how effective something is, in absolute terms.
OP might mean that because the protection isn't complete or permanent, it might not make sense for an otherwise healthy person to use it unless they expect to be in close quarters with a lot of possibly-sick people. Too early to say, ofc.
Almost nothing is 100% reliable or effective in biological systems. In this case, the initial promising results are from a small study in mice (check out OP's source). Anything could happen in the clinical trials.