Abstract
Virus/serum neutralisation test (VNT) of capripoxvirus (CaPVs) was studied to assess the post-vaccination (vaccine effectiveness) or post-infection antibodies level using two methods: alpha-VNT and beta-VNT which are generally carried out to measure the Neutralising Index (N.I.) and the serum Antibody titre (TAb) respectively. The authors have demonstrated that a positive correlation exists between N.I. and TAb values, this study aimed to add more evidence to this correlation by establishing a graph and its mathematical equations. We found that: N.I. = (1.489 Log TAb) + 1.331; this serves as a base to calculate N.I. using TAb values measured by beta-VNT without going through alpha-VNT and vice versa. At the end of this study we evaluated the equation accuracy by two parameters; the deviation (d) and the error percentage, which were d=0.2 and error (%) = 8% respectively.

Key words: Capripoxvirus, vaccine effectiveness, RM65 strain, Virus Neutralisation Test, Embryonic Lamb kidney Cells.