ABSTRACT
The development and use of vaccines in vaccination programs has been evolving over centuries (College Physicians of Philadelphia 2015). The term vaccination was coined when Edward Jenner (1796) used cowpox virus lesions from a cow to protect milkmaids against smallpox. Following this observation, the word vacca (Latin for cow, hence, vaccination) was coined. Today, vaccination is considered to be the most efcient method of preventing and eradicating infectious and contagious diseases of humans, livestock, and domesticated animals. Vaccines are also being targeted as an intervention against cancers, inammatory diseases, and allergies. Given the current drive to reduce use of antibiotics, vaccine development and usage is gaining momentum as a “green” preventative option. However, vaccines need to be safe, efcacious, and affordable. In addition, vaccines must rapidly induce a protective immune response in the host that mirrors protective immune responses induced following recovery from natural exposure. Vaccine efcacy can be inuenced by the characteristics and quality of the antigen, formulation, dosing regimen, site of vaccination, and method of delivery. Vaccines broadly fall into three categories: modied live (which are attenuated
17.1 Introduction .......................................................................................................................... 389 17.1.1 Vaccines Background ............................................................................................... 389 17.1.2 Pathogen-Host Interactions and the Immune Response ..........................................390
