Professor Saltzman continues his presentation on the topic of vaccine. First, Professor Saltzman describes the host immune response to pathogen recognition, in terms of immunoglobulin release, T-cell activation, and memory cell production. The production, distribution, and challenges involved in making of the Salk polio vaccine and the modern, oral polio vaccine are discussed. Professor Saltzman then talks about the range of bioengineering approaches that can be used to produce vaccine: attenuated, subunit, and DNA-based. Finally, a life-intervention cost analysis (cost of technology per human life saved) for vaccine was compared to other policies to further emphasize the impact of vaccine on improving public health worldwide.