Objective: To evaluate alterations in lymphocyte subpopulations, CBC results, and clinical signs in neonatal calves inoculated with 3 commercially available proprietary multiple-antigen vaccines containing known quantities of endotoxin.
Design: Prospective, randomized controlled field trial.
Animals: 36 healthy Holstein heifer calves between 3 and 31 days old.
Procedure: Vaccines were administered to 18 calves according to label instructions, except for the recommended age of administration. The 18 other calves served as unvaccinated controls. Two weeks after entry into the study, calves were given secondary doses of the same vaccines. Calves in both groups were examined and blood samples were collected for determination of lymphocyte subpopulations and hematological parameters once daily for 5 days beginning on the day that both the primary and the secondary vaccinations were given. Lymphocyte subpopulations, including BoCD2+, BoCD4+, BoCD8+, B cells, and gamma/delta T cells, were determined by use of flow cytometry, using monoclonal antibodies as markers.
Results: Vaccinated calves did not develop clinical signs of illness. There were no significant differences in absolute numbers of lymphocyte subpopulations between vaccinated and unvaccinated calves. Vaccinated calves had significantly higher rectal temperatures, total WBC counts, and absolute neutrophil counts than did control calves. These differences persisted for 3 to 4 days after vaccination.
Clinical implications: Findings confirm empirical observations that vaccination with multiple products at the same time may induce evidence of an inflammatory response in most calves. Additional research is indicated to further evaluate the safety of using multiple vaccines simultaneously.