susceptible host, a series of coordinated events must rcumvent both innate and adaptive immunity. One of the first and most important features of host innate immunity is the barrier provided by the epithelial surfaces of the skin and the lining of the gut. The difficulty of penetrat- ing these epithelial barriers ensures that most pathogens never gain productive entry into the host. In addition to pro viding a physical barrier to infection, the epithelia also pro duce chemicals that are useful in
the early vaccination trials of Edward Jenner and oneering efforts, vac nce of diseases such ng cougl Vaccination with DN A Active and Passive Immunization Designing Vaccines for Active Immunization mWhole-Organism Vaccines Purified Macromolecules as Vaccines Recombinant-Vector Vaccines DNA Vaccines Multivalent Subunit Vaccines mmon usage. Experience has shown that not every vaccine
