Swine Flu (Influenza A H1N1) Follow on Vaccine Study

We intend to recruit all interested participants who completed the original NIHR funded study (NCT00980850)(1) (n=937) into groups 1 & 2 outlined in table one above. It is anticipated that approximately 66% of these participants are likely to take part in this follow-on study; therefore the study population for groups 1 & 2 is likely to be approximately 560 children. As the option of only having a blood sample taken at visit 1 will be made available to participants in this study, there will be two cohorts of participants: the 'persistence' cohort (consenting to the baseline blood test alone) and the 'booster' cohort (consenting to the baseline blood test, seasonal influenza vaccine and post-immunisation blood test).

Inclusion Criteria:

The participants must have completed the original NIHR funded study (NCT00980850)(1) comparing Celvapan with Pandemrix at one of the study sites participating in this follow-on study.

A parent/legal guardian has given written informed consent after the nature of the study has been explained.

Willingness to either

1. undertake a blood test at visit 1 ('persistence' cohort)
2. complete all study procedures ('booster' cohort)

Exclusion Criteria:

Participant(s) in original study (NCT00980850)(1) who had a suspected unexpected serious adverse reaction (SUSAR).

Participants in the original study (NCT00980850)(1) who did not receive two doses of H1N1 influenza vaccine.

Participants in original study (NCT00980850)(1) who received a third dose of H1N1 influenza vaccine due to an inadequate response to two doses.

History of severe allergic reaction after previous vaccinations or hypersensitivity to any seasonal influenza vaccine component.

Current egg allergy.

Known or suspected impairment/alteration of the immune system.

Disorders of coagulation.

Immunosuppressive therapy, use of systemic corticosteroids for more than 1 week within the 3 months prior to enrolment.

Receipt of blood, blood products and/or plasma derivatives or any immunoglobulin preparation within 3 months prior to enrolment.

Previous receipt of, or intent to immunize with, any other seasonal influenza vaccine(s) throughout the 2010/2011 influenza season.

Participation in another clinical trial of an investigational medical product.

Any condition which, in the opinion of the investigator, might interfere with the evaluation of the study objectives. Children with chronic, stable medical illnesses that do not result in immunosuppression (e.g. cerebral palsy, epilepsy, cystic fibrosis, congenital heart disease) will be allowed to participate in the study, unless these conditions will in some way interfere with the completion of study procedures. Children with conditions that may alter the immune response to vaccines (e.g. Trisomy 21) or will affect the ability to accurately describe adverse events (e.g. children over 5 years of age but with severe learning difficulties) will be excluded.