ou are having lunch with a friend in early fall. Your work has recently announced that the annual flu shot clinic will be happening that afternoon, and you mention that you are planning to go. Your friend says she got the shot a couple years ago so should be good to go. Given your recent study of viruses and vaccines, you tell your friend the following (include in your answer an overview of both why she should get the vaccine this year, and a description of what a vaccine actually is - in your answer, include and describe the terms 'envelope' and 'attenuation').