Abstract: The nucleotide sequence of the P2 gene and the derived amino acid sequence of the P2 protein of Haemophilus influenzae type b are disclosed and the methods used to determine the same. Also disclosed are the methods used to clone and express the P2 gene as well as the purification protocol for the gene and protein. Also disclosed is the synthesis of peptides corresponding to the N-terminal and C-terminal ends of the P2 protein. Also disclosed is the use of the P2 protein as a protective agent for the disease caused by Haemophilus influenzae type b and the use of the protein as a carrier for conjugation with an oligosaccharide derived from Haemophilus to generate a potentially efficacious vaccine against the disease. Also disclosed is the use of P2 peptide-conjugates as immunising agents.