Every year, scientists develop influenza vaccines to help protect people from contracting the flu. However, the flu virus constantly evolves, so the vaccines must change accordingly.
Recommended Videos
How are flu vaccines made?
There are three main ways to make flu vaccines:
- Egg-based vaccines: This is the oldest and most common method. Scientists put flu viruses into fertilized chicken eggs and let the viruses grow. Then, they extract the virus from the eggs and either kill it to make a flu shot or weaken it to make a nasal spray vaccine. This method requires many eggs and takes some time.
- Cell culture vaccines: Instead of eggs, scientists grow the flu viruses in special cells in a lab. This method doesn’t need eggs and can be faster.
- Recombinant vaccines: This is the newest way. Scientists don’t use the whole virus at all. Instead, they take a tiny part of the virus’s genetic code and use it to make the vaccine in a lab. This method is the fastest.
All vaccines are thoroughly tested to ensure they are safe before people receive them.
How do scientists pick which flu viruses go in the vaccine?
The flu virus changes a lot because it can mutate (make small changes) or mix with other flu viruses. That’s why the vaccine has to be updated every year.
To track these changes, scientists worldwide collaborate through the Global Influenza Surveillance and Response System (GISRS).
This network includes 152 National Influenza Centers in 129 countries. These centers collect flu virus samples from people who are sick year-round. They study the viruses to see which types are spreading, how they are changing, and if they might cause more illness.
The network also has five special WHO Collaborating Centers located in the United States, the United Kingdom, Japan, China, and Australia. These centers conduct more detailed research on flu viruses and help guide vaccine decisions.
Scientists from all these centers share information and work together to watch the flu viruses closely.
Twice a year, experts from this global network meet to decide which flu viruses should go in the vaccine for the next flu season. They meet in February to select strains for the Northern Hemisphere (such as the U.S. and Canada) and in September for the Southern Hemisphere (such as Australia).
After they pick the virus strains, vaccine makers start making the shots. It takes about nine months to make enough vaccines for everyone.
Why are flu vaccines important?
Flu vaccines might not prevent everyone from getting sick, but they do help a lot. They make it less likely for people to get very ill or go to the hospital.
Even if the vaccine isn’t a perfect match for the flu circulating, it still helps protect people and slow the spread of the virus.