  In this paper, we study the construction of the supersymmetric extensions of
vertex algebras. In particular, for $N = n \in \mathbb{Z}_{+}$, we show the
universal enveloping $N = n$ supersymmetric (SUSY) vertex algebra of an $N = n$
SUSY Lie conformal algebra can be extended to an $N = n' > n$ SUSY vertex
algebra.
