Friday, April 20, 2012

Flu Fridays: How is the flu shot made? (Part 2)

Happy Flu Friday!

In our previous Flu Friday post, we talked about the process of deciding what types of flu will be covered by the seasonal flu shot. Today, we’ll take a closer look at how the shot is made each year. But first, here’s a little background on how vaccines protect you from diseases.

Vaccines work by tricking your body into thinking it has an infection. This is because vaccines contain dead or weakened forms of the bacteria or virus that they are trying to protect you from. Even though these bacteria or viruses are too weak to make you sick, when your body notices these invaders, the immune system kicks in. Your body builds up defenses against the invaders so that when you come in contact with a full-strength virus such as the flu, your body already knows how to fight it off.

There are two ways to get your flu vaccination: Via a shot or a nasal spray. Flu shots have inactive — or dead — viruses, while the nasal spray form of the vaccine contains weakened viruses. Whether you get your vaccine in a shot or a nasal spray, the vaccine helps your body prepare to fight the most common strains of flu each season.

But back to the making of the flu vaccine: As we discussed previously, seasonal flu vaccines contain three strains of viruses. After the strains of flu are chosen, scientists then have to grow enough of the viruses to make millions of doses of the flu vaccine that are used every year. This process can take up to six months or more because the viruses are grown in a very delicate place: The inside of a chicken egg!

[Flu researcher inserting virus into a chicken egg.
Image courtesy CDC/Taronna Maines]
In the lab, viruses are injected into each egg, and then the eggs sit at a perfect temperature for the virus to spread. After a few days, the viruses are removed from the egg and killed. Proteins from the dead virus are separated out. It’s these proteins that go into your flu shot. (Even if you have an egg allergy, the flu vaccine is probably safe for you — here’s why:

Labs around the world start working on the vaccines during the summer months so that the seasonal flu vaccine is ready to go by the start of the flu season in the fall or winter. After you get your flu shot, it takes a few weeks for your body’s immune system to protect you from the flu, which is why it’s best to get your seasonal flu vaccine as soon as it becomes available!

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