20 volunteers will be recruited in this study. They will all be adults over the age of 18. Volunteers will be assigned to one of two groups. Volunteers in group 1 will receive Viroflu, followed by a dose of MVA NP+M1. Volunteers in group 2 will receive Viroflu followed by a placebo injection (saline). Volunteers will be blinded so that they do not know which group they have been allocated to and will be asked to complete diary cards listing any adverse events after vaccination.