The stimulation of PBMCs from S96 vaccinates was clearly significantly increased over 0 dpv at 14, 21 and 28 dpv, whether the stimulus was homologous (S96 antigen) or heterologous (N75 antigen) ( P ≤ 0.0003 for all comparisons).
In cells from N75 vaccinates, there appeared to be a slight increase in the percentage of PPRV-specific CD4 + T cells, but the change did not reach statistical significance.
While the N75 and S96 vaccine strains are effective, they are derived from viruses isolated 43 and 22 years ago, respectively, and there may be significant genetic drift between these strains and those circulating now.