Flu Fridays: How is the flu shot made? (Part 1)

Happy Flu Friday! Here at Get Ready, we spend a lot of time talking about the importance of getting your flu shot every year. But have you ever wondered how the vaccine is made?

There are actually two parts to making a flu shot: First, experts decide what types of flu will be included in the flu shot for the next year. Then, vaccine manufacturers start making the flu shots so that by the time the next flu season starts, millions of doses will be available. Today we’ll talk about the first part of the question: How do they decide what goes into a flu shot?

Image courtesy
CDC/ Doug Jordan, M.A.

Every year, in more than 100 countries around the world, health workers and scientists collect samples from people who are sick with the flu. These samples are sent to five international labs, chosen by the World Health Organization, that test the samples and find out what strains of influenza are most common. (In case you were wondering, the five labs are in the U.S., England, Australia, China and Japan.)

In the beginning of the year, WHO calls a big meeting with all of these international flu researchers. They figure out which types of influenza viruses were most common over the past year and then decide which strains should be included in the next seasonal flu shot. The formulas can change every year, which is why it is important that you get a new flu shot every season.

This big WHO vaccine composition meeting just happened in February. Participants decided that next year’s flu shots should protect people against two kinds of influenza A, H1N1 and H3N2, and one kind of influenza B. To learn about the difference between influenza A and B, check out our blog post about what causes the flu. You can also learn more about the vaccine selection process from the Centers for Disease Control and Prevention.

Once WHO makes its recommendations, vaccine companies around the world start making flu vaccines for the next season. While WHO recommends specific vaccine viruses for vaccine production, each country makes its own decision for vaccine licensing in its country. Making the new vaccine can take six to nine months, which means that companies are already starting to make your flu shot for next year!

Want to learn more? Check out Part 2 on how the flu shot is made, where we take a closer look at the flu shot manufacturing process.