A method of preparing a recombinant influenza vaccine using DNA technology is provided. The resulting vaccine is a multivalent, preferably trivalent, influenza vaccine based on a mixture of recombinant hemagglutinin antigens cloned from influenza viruses having epidemic potential. The recombinant hemagglutinin antigens are full length, uncleaved (HAO), glycoproteins produced from baculovirus expression vectors in cultured insect cells and purified under non-denaturing conditions. The recombinant vaccine can be developed from primary sources of influenza, for example, nasal secretions from infected individuals, rather than from virus adapted to and cultured in chicken eggs. The process for cloning influenza hemagglutinin genes from influenza A and B viruses uses specially designed oligonucleotide probes and PCR. In the preferred embodiment, the cloned HA genes are then modified by deletion of the natural hydrophobic signal peptide sequences and replacing them with a new baculovirus signal peptide.