In a two-step scheme, specialty vaccine developer Paxvax Inc. acquired the FDA-approved oral typhoid vaccine Vivotif from Crucell Switzerland AG and financed the deal with $50 million in secured debt from an investment fund managed by Pharmakon Advisors and $12 million in an extension of its series B preferred stock. The Redwood City, Calif.-based company, whose lead product is a single-dose cholera vaccine in a phase III program, now takes up the challenge of transforming from a small biotech to a commercial venture.