Final answer:
The central idea of the text 'What is a Vaccine?' by Lindsey Konkel is to provide a better understanding of science and its relationship to human health, with a focus on the effectiveness of vaccines in preventing diseases and addressing common concerns.
Step-by-step explanation:
The central idea of the text 'What is a Vaccine?' by Lindsey Konkel is to provide a better understanding of science and its relationship to human health. The text discusses the effectiveness of vaccines in preventing diseases like flu, measles, and polio, and addresses common concerns such as the alleged link between vaccines and autism. It also examines the reasons why diseases that were once common have become rare and why vaccination is still necessary.