  We prove moderate deviation principles for the tagged particle position and
current in one-dimensional symmetric simple exclusion processes. There is at
most one particle per site. A particle jumps to one of its two neighbors at
rate $1/2$, and the jump is suppressed if there is already one at the target
site. We distinguish one particular particle which is called the tagged
particle. We first establish a variational formula for the moderate deviation
rate functions of the tagged particle positions based on moderate deviation
principles from hydrodynamic limit proved by Gao and Quastel
\cite{gao2003moderate}. Then we construct a minimizer of the variational
formula and obtain explicit expressions for the moderate deviation rate
functions.
