Given the reluctance of RAF aircrew medicals to accept individuals who have had laser eye surgery for example, I wouldn't hold your breath for them accepting a brand spanking new allergy vaccination.
It comes down to the risk of accepting someone with an illness that could ultimately risk their life (or that of their crew/passengers, the very expensive equipment or people on the ground etc), even if the odds are very small.
The best thing you can do is keep an eye on developments of the vaccine and at an appropriate time apply for OASC and see what they say (and read the OASC thread on the Mil Aircrew forum too). Good luck.