A lower bound for the order parameter in the one-dimensional contact process

It is shown that [varrho]([lambda]) >= (1 - [lambda]c/[lambda])(2[lambda]2 + 3[lambda] + 2)/(([lambda]2 + [lambda])(1 + [lambda]c)), where [lambda]c is the critical value and [varrho]([lambda]) is the order of the one-dimensional contact process with parameter [lambda]. An implication of this inequality for vaccination policies for epidemic diseases is discussed.