Description:
<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Dexamethasone is routinely administered to horses but its effect on the antibody response to a commercial EIV/EHV vaccine is unclear.</jats:p></jats:sec><jats:sec><jats:title>Hypothesis</jats:title><jats:p>Horses receiving dexamethasone will have lower postvaccination antibody levels against EIV and EHV‐1 than vaccinated controls.</jats:p></jats:sec><jats:sec><jats:title>Animals</jats:title><jats:p>Fifty‐five healthy adult research horses.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Randomized cohort study. Control (no vaccine, group 1), vaccination only (EIV/EHV‐1/EHV‐4, Prestige 2, Merck Animal Health, group 2), vaccination and concurrent single intravenous dose of dexamethasone (approximately .05 mg/kg, group 3), vaccination and 3 intravenous doses of dexamethasone at 24 hours intervals (group 4). Serum SAA levels were measured on day 1 and day 3. Antibody levels against EIV (hemagglutination inhibition assay, Kentucky 2014 antigen) and EHV‐1 (multiplex ELISA targeting total IgG and IgG 4/7) were measured on day 1 and day 30.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Significantly increased mean antibody titers after vaccination were only noted against EIV and only after the vaccination alone (n = 14, prevaccine mean [prvm] 166.9, SD 259.6, 95% CI 16.95‐316.8; postvaccine mean [povm] 249.1, SD 257.2, 95% confidence interval [CI] 100.6‐397.6, <jats:italic>P</jats:italic> = .02) and the single dose dexamethasone (n = 14, prvm 93.14, SD 72.2, CI 51.45‐134.8; povm 185.1, SD 118, CI 116.7‐253.6, <jats:italic>P</jats:italic> = .01), but not after multiple doses of dexamethasone (n = 14, prvm 194.3, SD 258.3, CI 45.16‐343.4; povm 240.0, SD 235.7, CI 103.9‐376.1, <jats:italic>P</jats:italic> > .05).</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>The effect of dexamethasone on the postvaccine antibody response varies depending on the dosing frequency and the antigen‐specific antibody type.</jats:p></jats:sec>