Did you get a flu shot this year?For the first time,the Centers for Disease Control and Prevention in the US is recommending that all children aged from 6 months to 18 years receive the flu _ . Vaccines battle diseases caused by bacteria and viruses.A weakened form of the germ   is introduced into the body.The body makes special substances called antibodies   to fight the germs.If the actual germs were to attack,the antibodies would fight.Because there are many kinds of flu viruses,scientists must create a new vaccine formula   each year.Researchers must make a prediction. It is like forecasting the weather.Sometimes they are right on,and sometimes they are off.But even when the vaccine does not closely match circulating flu types,it can make the illness less serious. "The flu vaccine is not as effective as the polio   vaccine or the measles vaccine," says Dr.William Schaffner of Vanderbilt University School of Medicine."It's not a great vaccine,but it is in fact quite a good vaccine." But a flu vaccine doesn't work for everyone.There are certain people who should be careful about taking it,because the vaccine is produced in eggs.Those who are allergic   to eggs should not take it.If you have a fever,you should wait until you recover. Some people are afraid that they might get the flu from the flu shot.Scientists say that it is not possible,because the viruses in the flu shot are inactivated.But some minor side effects such as lowgrade fever and body ache could occur.If they do,they begin soon after the shot and usually last only one to two days. Did you know?Smallpox was the first disease people tried to prevent by putting a virus into a healthy person.In 1796,English scientist Edward Jenner placed some infected material under a boy's skin. By saying "It's not a great vaccine,but it is in fact quite a good vaccine." (in Para.4),William Schaffner means the flu vaccine  _  .
is as effective as the polio and the measles vaccines is worse,compared with the polio and the measles vaccines does help to make illness less serious is quite good because it works for everyone