Millions of Americans are vaccinated each year, whether they are elders looking to avoid bouts of influenza or children whose parents want to protect them from potentially deadly childhood diseases. Still, there remains a vocal segment of the population in opposition to all immunization, some even refusing to get mandated vaccinations for their children. Here, a specialist of internal medicine explores that paradox. Dr. Link explains the immune system and how it works, as well as the history of vaccine development, and the various types of vaccines including the efficacy and potential toxicity of each. A physician for more than 35 years, Link also spotlights possible future vaccines, such as those being developed in the hope of immunizing against HIV. Appendices to this work spell out current medical recommendations for vaccines, describe the legal issues involved in decisions to vaccinate or not, and explain the workings of clinical trials where work is done to determine if a vaccine is effective or not, or has any remarkable side effects. A strong supporter of vaccination programs, Link says that all people should understand the powers, limitations and risk of immunization.