An SIRS epidemic model with general periodic vaccination strategy is analyzed. This
periodic vaccination strategy is discussed first for an SIRS model with seasonal variation in
the contact rate of period T= 1 year. We start with the case where the vaccination strategy
and the contact rate have the same period and then discuss the case where the period of the
vaccination strategy is LT, where L is an integer. We investigate whether a periodic
vaccination strategy may force the epidemic dynamics to have periodic behavior.