How effective is the flu vaccine?

In the event of exposure, the vaccine prevents 'flu in up to 90% of young adults, but in only 30-40% of the elderly.

However, it does reduce severe disease in the elderly, thus decreasing hospitalisation, and reduces the risk of death by 80%.

The flu vaccine is effective for eight to 12 months. This is one reason why it has to be repeated every year. (The other is because of the changing 'flu strains.)

Reviewed (2006) by Dr Jane Yeats MBChB, BSc(Med)(Hons)Biochem, FCPathSA(Virology).