History of influenza vaccination – World Health Organization

We know now that influenza, or flu, is caused by a virus but formany years it was thought to be caused by a bacterial infection. In 1892, German scientist Richard Pfeiffer isolated a small bacterium from the noses of patients with flu, naming it bacillus influenzae.

Early attempts at a vaccine during the 1918 influenza pandemic were based on this understanding, and it was not until the 1930s, when the influenza virus was identified, that progress towards an effective vaccine could really begin.

Influenza also known as the flu is a highly contagious respiratory illness, which spreads easily through the air or when people touch contaminated surfaces. In many cases the disease is mild, with symptoms such as chills,fever and fatigue, and it can also be spread through asymptomatic infections in people who do not even know they are sick.

But the flu can also result in serious complications, particularly in vulnerable people like young children, older persons, pregnant women and people with medical conditions such as asthma, diabetes or heart disease. The most common complication ispneumonia, typically caused by a secondary bacterial infection.

Flu viruses mutate very rapidly, and uncontrolled spread gives rise to many different strains, which fall into 2 main types affecting humans influenza A and influenza B.

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History of influenza vaccination - World Health Organization