A method for formulating an immunologically active agent and an apparatus for delivery same, the method comprising the steps of providing a bulk immunologically active agent, subjecting the bulk immunologically active agent to tangential-flow filtration to provide an immunologically active agent solution, adding at least one excipient to the agent solution and spray-drying the agent solution to form an immunologically active agent product; the apparatus comprising a microprojection member that includes a plurality of microprojections having a biocompatible coating disposed thereon that includes a spray-dried immunologically active agent. In a preferred embodiment, the immunologically active agent comprises an influenza vaccine, more preferably, a split-varion influenza vaccine.