Experts advise that everyone 6 months of age and older get a flu shot this year. Learn what vaccines do and how they're made.

Government experts at the Centers for Disease Control and Prevention (CDC) advise that everyone 6 months of age and older get the flu shot when it's available this fall. This year, one vaccine will protect you from both the seasonal and swine flu viruses.

If you're thinking about getting a flu shot, it may help to understand a little more about vaccines and what they do.

How do vaccines work?
When a new disease-causing germ (or microbe) enters your body, it normally takes about a week for your immune system to fight it off. During this time you get sick. But next time that same microbe comes around, your immune system is ready for it. You probably won't get as sick because you have built up an immunity to it.

Vaccines were developed to help protect people from serious or life-threatening diseases. A vaccine gives your immune system the ammunition to attack microbes before they can make you sick.

Vaccines are usually made from parts of microbes or whole microbes that are killed or weakened. They give your body a chance to fight a similar but harmless opponent and acquire immunity to it. If the real disease comes along, your body is ready to fend it off.

How are vaccines made?
Making flu vaccines is a long, complex process. It often takes about a year to make the seasonal flu vaccine that becomes available each fall.

Flu vaccines are usually grown in fertilized chicken eggs. The virus is injected into an egg. It is allowed to multiply in the embryo for several days. Then the egg is opened and the virus is harvested. After being purified and inactivated, it is used to make vaccine.

Are vaccines safe?
Vaccines are very safe and usually cause only mild side effects. But no vaccine can be 100 percent safe or effective because people's immune systems are so different. Still, the rate of adverse reactions to vaccines is usually very low.

Vaccines are one of our best tools for stopping a disease epidemic or pandemic. People who get vaccines usually don't get sick. If they do, their illness is usually mild. Vaccines are also very important to help protect people like young babies or others who may not be able to get the vaccine. If the people around them get vaccinated, these at-risk people are much less likely to get sick.