  A non-degenerate contact form is lacunary if the indexes of every
contractible periodic Reeb orbit have the same parity. To the best of our
knowledge, every contact form with finitely many periodic orbits known so far
is non-degenerate and lacunary. We show that every non-degenerate lacunary
contact form on a suitable prequantization of a closed symplectic manifold $B$
has precisely $r_B$ contractible closed orbits, where $r_B=\dim
\mathrm{H}_*(B;{\mathbb Q})$. Examples of such prequantizations include the
standard contact sphere and the unit cosphere bundle of a compact rank one
symmetric space (CROSS). We also consider some prequantizations of orbifolds,
like lens spaces and the unit cosphere bundle of lens spaces, and obtain
multiplicity results for these prequantizations.
