Single dose vaccination with AS03-adjuvanted H5N1 vaccines in a randomized trial induces strong and broad immune responsiveness to booster vaccination in adults

Priming a population with a pre-pandemic vaccine is being considered to maximize the response upon subsequent vaccination with a true pandemic vaccine more closely matched to the causative pandemic strain. The present study explored this prime-boost concept by evaluating different primary schedules with the pre-pandemic A/Vietnam/1194/2004(NIBRG-14) vaccine, containing 3.75 microg of HA, followed by a 6-month booster with a vaccine formulated with 3.75 microg HA of either the same strain or with A/Indonesia/05/2005(IBCDC-RG2), a heterologous strain from a different clade. In this multicentre, open, randomized study (NCT00430521) we measured immune responses in four groups (N = 48-60) of adu…