A highly potent pneumo-3 vaccine of combined inactivated Bovine viral diarrhea virus types 1 (BVDV-I), bovine herpesvirus type 1 (BHV-I) and parainfluenza 3 virus (PI3V) could play a valuable role in respiratory disease control program in calves. We determined the influence of virus concentration by polyethylene glycol (PEG) precipitation on the immune response of calves to the inactivated pneumo-3 vaccine. Both the concentrated and commercial pneumo-3 vaccine was administered twice to six month old seronegative calves through intramuscular (IM) route. Different doses, 2ml, 2.5ml and 3ml of the concentrated vaccine were tested compared with 5ml for the commercial pneumo-3 vaccine. The induced BVDV-I, BHV-I, PI3Vantibodies were followed up in the sera of vaccinated calves up to 24 week post vaccination (wpv) using serum neutralization test (SNT) and indirect enzyme linked immune sorbent assay (ELISA). Virus concentration had a significant effect on serum antibody levels by the 2nd wpv till 24th wpv as well as the economy of the vaccine, where the same immunological effect for the commercial vaccine produced by half dose (2.5ml) of our concentrated pneumo-3 vaccine.