Vaccines (疫苗) help keep you healthy. How do vaccines help you keep healthy? The vaccines are made from bacteria (细菌)that causes the illness. A little bit of bacteria isn't enough to make you sick. But it is enough to make your immune system(免疫系统) active.
While some vaccines are a lifetime, others wear off after a few months or years. Most doctors suggest the following vaccines: measles-mumps-rubella, hepatitis B and chicken pox. After these vaccines when you are very young, you will be far away from most of these diseases all your life.
Joe's flu vaccine will be good for about six months to a year. His doctor explained why. "When I give a flu shot(注射), "Dr. Smith said, "I put a bit of flu bacteria into your body. You build up antibodies(抗体) against this bacteria. But this vaccine won't protect you once (一旦) the bacteria has changed. That's why you will have to get a new one before the flu season hits next year."
"I had the flu last year," Joe said. "I was really sick. I missed a whole week of school. When I did go back, I still didn't feel really great. I couldn't even play basketball for another week after that. I guess it's worth (值得…的) getting a flu shot every year. "
Are you protected? That shot is so much easier than getting one of these serious illnesses.
