Outcomes in different populations may vary, and further research is needed, but the results of one study suggest that oral amoxicillin-clavulanic acid or doxycycline outperform a single injection of cefovecin. Possible factors to consider include issues of handling stress, digestive upset, and the prevalence of resistant organisms.
Litster AL, Wu CC, Constable PD. Comparison of the efficacy of amoxicillin-clavulanic acid, cefovecin, and doxycycline in the treatment of upper respiratory tract disease in cats housed in an animal shelter. J Am Vet Med Assoc. 2012 Jul 15;241(2):218-26.