T-cell Diversity Following Intranasal and Intramuscular Vaccines

The investigators will explore in an experimental medicine healthy human model of immunisation, whether switching the route of sequential administration of licensed influenza vaccines can result in an immune response that is broader in its ability to recognise different substrains of influenza viruses. The investigators will do this by initially giving an immunisation with a nasal or an injected vaccine, and then switching subjects over to receive a second dose one month later (when the cellular component of immunity will have matured) via the opposite route (nasal-\>injected or injected-\>nasal). The investigators will use research assays that can map the different parts of the influenza virus that the vaccinated person's immune cells recognise at baseline, after the first immunisation, and then again after the second, to see if the breadth of the recognition has broadened to include new strains or virus components. Should this pilot study give an indication that the breadth has widened (rather than just a further boost to the same responses seen after the first immunisation) it will provide justification for a larger study in which statistical significance may be powered for observed changes. The study is funded by ADITEC, which is a collaborative research programme that aims to accelerate the development of novel and powerful immunisation technologies for the next generation of human vaccines.