A man covers his eyes as he receives a flu shot

From Medical Correspondent Dr. Steve Salvatore

(CNN) -- Fall marks the season for the yearly flu shot. But for some people, there's more than a fear of needles that's keeping them away. It's myths that still persist about the vaccine's benefits and risks.

One of the biggest misconceptions is that flu shots cause the flu. A flu vaccine contains dead influenza virus that simple cannot make you sick.

The vaccine works by prompting a response from the body's immune system, which sometimes causes the achy feeling some people report after getting a flu shot.

Another myth is that flu shots don't work. Last year, despite their flu shots, many people got sick because of a strain of the flu that caught health experts off-guard. This rather virulent strain, called type A Sydney flu virus, is included in this year's vaccine.

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CNN's Dr. Steve Salvatore reports
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A majority of people in the United States do not get a yearly flu shot.

"I think in theory that if you could vaccinate everybody each year, then you could potentially cut down on the transmission of this virus," said Dr. Keiji Dukuda of the Centers for Disease Control and Prevention.

Experts say the vaccine is most important for those who could suffer serious consequences from the flu, such as the elderly, young children and those with weakened immune systems.

Only people allergic to eggs should be cautious since most flu vaccines are made with eggs.

If you heard there might be shortage of the vaccine this year, don't worry. Although one of the four major vaccine manufacturers had to delay shipment because of problems cultivating this year's strains of the virus, health officials say there is still plenty to go around.