When the Spanish influenza pandemic raged around the world in late 1918, medical science at first assumed that the disease was bacterial in nature and attempted to fight it with a bacterial vaccine. Researchers soon realised that its cause might instead be a ‘filter-passer’ (today’s ‘virus’); but amid the crisis bacterial vaccination was persevered with, in the hope that it would at least mitigate influenza’s severity, or subdue its complications. In countries like Britain and the United States, the pandemic’s onset was so overwhelming that vaccination programs could scarcely keep up. By contrast, in Australia the three months’ grace afforded by maritime quarantine enabled federal and state authorities to develop a bacterial vaccine and implement a public vaccination program before Spanish influenza entered the community. Modern medicine may be dismissive of efforts to tackle a viral disease by bacterial means; but the consensus of medical opinion at the time, borne out by statistical studies, was that the vaccine had indeed diminished influenza’s mortality in Australia. In retrospect, the research that produced the bacterial vaccine was itself a remarkable venture in the relatively new field of bacteriology, and both it and the pandemic contributed much to the emergence of modern virology.