Attenuated respiratory syncytial virus

An immunogenic composition comprising an attenuated respiratory syncytial virus selected from the group consisting of the viruses having ATCC Designation Nos. VR-2511, VR-2512, VR-2513, VR-2514, VR-2515, VR-2516, VR-2517, VR-2564, VR-2565, VR-2566, VR-2567, VR-2572, and derivative viruses of ATCC Designation Nos. VR-2570 and VR-2571, wherein the derivative viruses are characterized by having a codon encoding an amino acid in the F protein chosen from the group consisting of a codon encoding isoleucine at amino acid 40, a codon encoding glutamic acid at amino acid 66, a codon encoding alanine at amino acid 76, a codon encoding isoleucine at amino acid 79, a codon encoding threonine at amino acid 97, a codon encoding phenylalanine at amino acid 119, a codon encoding isoleucine at amino acid 129, a codon encoding lysine at amino acid 191, a codon encoding glycine at amino acid 235, a codon encoding arginine at amino acid 235, a codon encoding lysine at amino acid 294, a codon encoding glutamic acid at amino acid 294, a codon encoding glutamic acid at amino acid 298, a codon encoding alanine at amino acid 298, a codon encoding threonine at amino acid 357, a codon encoding valine at amino acid 368, a codon encoding aspartic acid at amino acid 368, a codon encoding isoleucine at amino acid 384, a codon encoding leucine at amino acid 398, a codon encoding serine at amino acid 398, a codon encoding alanine at amino acid 522, a codon encoding methionine at amino acid 530 and combinations thereof.