You Can’t Get the Flu From the Flu Shot, Here's Why...

It is that time of year again.  The clinic has flu vaccine so we are now scheduling. This post was originally in 2011. #in

Many parents and patients have questions about the flu shot. One of the common questions we hear in the office: “Is it possible to get the flu from the flu shot?” It’s a fair concern. After all, you’re bringing your child to the doctor to get them or keep them well, not to cause more harm. If we give you a vaccine, you should feel comfortable that it is a safe one, especially if it’s one we want to give your child every year.

So here’s the full story on the flu vaccine: I have to start by defining flu. The term is used to mean many different illnesses. When we talk about the flu shot, we are referring to the influenza virus. The main symptoms of infections with this virus are fever, body aches, runny nose and cough. Some people with have mild vomiting or diarrhea with influenza, but it should not be confused with what people call the stomach “flu” where vomiting and diarrhea are the primary symptoms.

Okay, now onto the vaccine. The influenza vaccine has been made the same way for many decades. Each year around February, the World Health Organization looks at which strains are circulating around the globe and tries to make an educated guess as to which strains are expected the following year. Most years there are two of the A strains and one B strain of the virus in the vaccine. Because viruses can only grow inside of living cells, chicken eggs are infected with influenza virus.

After the virus has had time to reproduce it is purified away from as much of the egg parts as possible, leaving just reproduced influenza. The virus is then broken up, mixing up all the pieces using a detergent. Next comes the step that makes it impossible to get the flu from the flu shot. Two proteins from the surface of the virus are purified away from all other parts of the virus. These two purified pieces of the virus are then put into a sterile solution to keep them stable. The result: the flu vaccine.

These purified pieces of the virus are not capable of causing any infection. It would like going to the junk yard and getting a few windshields and a few steering wheels and then have someone claim it could run you over. The parts just aren’t there. This system makes it so it is 100% impossible to get the flu from the flu vaccine.

The purified pieces can protect you from the flu, though. When the proteins are injected, the body recognizes them as foreign and the immune system makes antibodies to clear them out. The antibodies are kept around for many months so that if you pick up an influenza virus at the mall in January; your body is already to fight it off before it makes you sick.

It is possible to have side effects from the shot. After all, we are trying to fool the immune system into reacting to these proteins as if they were an invader so the body sometimes acts like it is being invaded for a few days. Common side effects are soreness at the injection site, mild achiness and possibly a fever for a day or two, a small price to pay for protection from a virus that kills about 20,000 Americans each year.

Re-blogged from by Jay Rosenbloom MD PhD of PortlandPediatrics.