The present invention describes an immunogenic formulation to be used in mammals against the respiratory syncytial virus (RSV), consisting in the Calmette-Guérin bacillus (BCG) strain or other attenuated Mycobacterium strain that expresses heterologously at least one protein or immunogenic fragment of the RSV subtype A or RSV subtype B strains, originated from proteins NS1, NS2, N, P, M, SH, M2 (ORF1), M2 (ORF2), L, F or G. The genetic material that encodes for these proteins or immunogenic fragments is inserted into the BCG genome or extrachromosomally in one or several copies, which expression is regulated by endogenous or exogenous BCG promoters, either constitutive or inducible. The viral proteins or immunogenic fragments can be expressed by BCG as cytoplasmic-soluble, extracellularly-secreted or cell membrane-bound proteins. The preparation can further contain combinations of previously described formulations. The formulation can be stabilized by freeze-drying (conservation range from 4° C. and 25° C.) or through low temperatures (−80° C.) in a buffered saline solution to be conserved prior to its use.