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.