Can the flu shot make you sick?

Influenza is a highly contagious and potentially deadly illness. In the United States alone, it kills roughly 36,000 people every year and hospitalizes more than 200,000 – which is why it's so important to get immunized. Viewers often write to me asking if they really need to get a flu shot, or if it will make them sick. If a person gets sick  after a flu shot, its probable that they were exposed to the flu prior to getting vaccinated. You see it takes about two weeks to build up immunity to the virus, so if you were infected before you got the shot, you could still get sick.

The Centers for Disease Control and Prevention offers some tips on who should and shouldn’t get vaccinated.

WHO SHOULD GET VACCINATED: Adults over the age of 50; all children between the ages of six months and 18 years;  pregnant women; healthcare workers

WHO SHOULD NOT GET VACCINATED: Children younger than six months; people allergic to chicken eggs; people with past allergic reactions to vaccines

The flu virus is airborne and you can catch it just about anywhere: talking to your neighbor, shaking hands with a colleague, or brushing against a railing at a football game. So be sure to wash your hands often to prevent infection.

Be sure to tune in to Dr. Sanjay Gupta every weekend on HOUSE CALL. You'll find the answers to your medical questions Saturday and Sunday at 8:30 a.m. ET on CNN.