Sir, – Maj Robert Gregory, the "Irish Airman" of WB Yeats's poem, could not have been given a flu vaccination in 1918 just before his final flight, as Frank McNally writes (An Irishman's Diary, January 13th). Influenza was only confirmed as a viral, not bacterial, illness in 1933 with the first vaccine becoming available in 1938.
Maj Gregory was probably inoculated with a bacterial vaccine which, though it caused his death, would have given no protection against Spanish flu.
One such bacterium would later be named Haemophilus influenzae, the name retaining the legacy of its long-standing, though inaccurate, association with influenza. – Yours, etc,
Dr JOHN DOHERTY,
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Vienna.