The current invention pertains to an aqueous composition containing a biological antigen and an acrylic acid polymer, wherein the composition comprises an electrolyte to provide an osmolarity higher than the osmolarity of a 0.9% (w/v) sodium chloride solution in water. The invention also pertains to the acrylic acid polymer for use in a one shot vaccine against porcine circo virus 2 (PCV2) and optionally Mycoplasma hyopneumoniae and in an aqueous composition for reducing fever induced by the biological antigens present in the aqueous composition when the composition is administered to a subject animal.
