Researchers in New York studied 414 children under 5 who developed influenza during the winters of 2003-4 or 2004-5 and their vaccination status was compared with over 5000 children who did not catch the flu.
Significant flu vaccine effectiveness was not evident in either of the seasons studied – there was an estimated range of effectiveness from 7-52% in fully vaccinated 6-59 month olds.
The study noted that the strains of the virus used in vaccines were not suitable. For example, in 2003-4 the influenza A virus was responsible for 99% of circulating strains and only 11% of vaccines contained the correct virus.
Authors wrote: ‘Further studies of influenza vaccine effectiveness are needed using a variety of study designs to assess the yearly impact of influenza vaccination programmes for children.
Archives of Pediatric Adolescent Medicine (2008): 943-951