Peptides used in this study.

NP and M2 peptides used in this study for analysis of immune responses. Amino acids in the challenge virus sequence which differ from the A/PR/8/34 sequence are underlined. Amino acids in the challenge virus sequence which differ from the A/Ann Arbor/6/60 sequence are bolded. aSource virus of the specified peptide. bProtein and sequence range of the peptide. cMice tested with the peptide. dSequence is 100% identical in vaccine and challenge viruses.