Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Flu Vaccine Won't Give You the Flu, Despite Repeated Claims

Dear Doctor: What is in the flu vaccine that makes people feel so bad? A co-worker of mine got a flu shot last year and wound up feeling quite ill. Can a flu shot give you the flu?

Dear Reader: No, you can't get the flu from a flu shot. The flu vaccine is made two ways. One type of vaccine is made from a virus that has been inactivated, also known as a "killed" virus. Another type of vaccine contains no virus at all.

That said, it's entirely possible to have a physical reaction to the flu vaccine. For some people, that's redness, pain and swelling at the injection site. For others, it's a few days of aches and pains, perhaps with a bit of fever. This second reaction, which can feel similar to a slight case of the flu, is quite likely how the misconception that the vaccine can give you the flu first arose. But those symptoms are actually your body's response to the immune system as it rallies to produce antibodies to the flu virus.

It's also possible to catch the flu in the two weeks after you get your flu shot. That's because it takes up to two weeks for the vaccine to offer full protection. During that time, if you're exposed to the flu virus, you can go on to become ill. And don't forget -- flu vaccines target the specific viruses that epidemiologists believe will be active during a given flu year. If you run afoul of a different virus than the ones your flu shot targets, it can make you sick. Another thing to remember -- flu symptoms like chills, high fever, coughing, sneezing and bodily discomfort are shared by a range of different illnesses, including the common cold.

Speaking of which, the flu -- we're really talking about influenza here -- is more than a particularly nasty cold. Thanks to advances in modern medicine, it's easy to forget that the influenza pandemic of 1918 killed between 50 and 100 million people worldwide. According to the Centers for Disease Control and Prevention, when adjusted for today's increase in population, that would equal 175 to 350 million deaths.

Today, flu deaths in the United States have dropped significantly to about 4,600 per year. However, the very young, the elderly, people with chronic diseases like asthma, diabetes and congestive heart failure, and those with compromised immune systems are at increased risk for developing serious complications. The flu virus can cause lung inflammation serious enough to lead to respiratory failure. It can also lead to pneumonia, bronchitis and infections of the ear or sinus. For those living with chronic health conditions, the flu can make them worse.

All of which, in our opinion, are strong arguments in favor of an annual flu shot. The CDC recommends everyone older than 6 months old get one. Here in the U.S., flu season is fall and winter, with the peak months typically running from November through March. That means we're in the thick of it right now.

If you haven't gotten your shot yet, it's fast, it's easy, and there are plenty of low-cost and even free flu shot clinics. And there's still plenty of time.

(Send your questions to, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)