They will be the first in the country to receive the vaccine.
The aim of the trial is to determine which vaccine is the most effective in children. The results will be used to inform the Government ahead of a possible vaccination programme in the autumn.
So far, swine flu vaccines have only been tested on adults.
Researchers from five centres will divide children into two groups to test either a vaccine made from an inactivated form of the whole swine flu virus, or one made from key components of the virus and a substance designed to stimulate the immune system.
They will be given two doses of the vaccine and a blood test before and after to see how their immune system responds. Researchers will also look at any side effects caused by the two vaccines, monitoring children's daily temperatures and reactions, such as injection site redness or swelling, for seven days after each immunisation.
The European Medicines Agency recommends that children are given two doses three weeks apart.
The study is being led by Andrew Pollard, professor of paediatric infection and immunity director at the University of Oxford (pictured). He said, 'Vaccines are the best way to protect against flu and should definitely be recommended for all children in high risk groups who have the greatest chance of serious disease.'
The study, sponsored by the University of Oxford and done in collaboration with the Health Protection Agency, is funded by the National Institute for Health Research (News, 3 September).
It comes a month before at-risk groups and frontline health workers are offered a swine flu jab.
Further information: www.swineflutrial.org.