Let AR,q denote a family of covering codes, in which the covering radius R and the size q of the underlying Galois field are fixed, while the code length tends to infinity. The construction of families with small asymptotic covering densities is a classical problem in the area Covering Codes.In this paper, infinite sets of families AR,q, where R is fixed but q ranges over an infinite set of prime powers are considered, and the dependence on q of the asymptotic covering densities of AR,q is investigated. It turns out that for the upper limit µ * q (R, AR,q) of the covering density of AR,q, the best possibility is(1)The main achievement of the present paper is the construction of optimal infinite sets of families AR,q, that is, sets of families such that (1) holds, for any covering radius R ≥ 2. We first showed that for a given R, to obtain optimal infinite sets of families it is enough to construct R infinite families A (0) R,q , A (1) R,q , . . . , A (R−1) R,q