Here is some info on vaccination against pmv.
https://journals.tdl.org/watchbird/index.php/watchbird/article/view/2526
My birds are not vaccinated but if pmv appeared in my loft I would consider it.
@Rabi Gabriel - Where are u located? U.K.? US? Is it winter or summer where you are?
Also, I just noticed that the link I posted gives 3 homeopathic remedies that may help with the symptoms. If you want to try meds I suggest the homeopathic remedies over the antibiotics. Antibiotics do not help...
I think it sounds most like PMV.
http://www.pigeon-aid.org.uk/pa/html/paramyxovirus__pmv_.php
I have no personal experience with this in my birds. It is a virus so there is really no treatment other than supportive care.
@Old_Strain_Lover has more experience than most of us so I would defer to...