We spend a lot of time each fall talking about influenza and flu vaccine. A great deal of hard work by very smart people goes into making this magic fluid each year.
The first thing you need to make flu vaccine is a flu virus. Those come in many different flavors, some old standbys trying to make a comeback, occasionally some new virus. Because the earth is tilted, our summer is the Southern Hemisphere’s winter. They are having this year’s flu season 6 months before we do. The best place to look for new influenza viruses are poor rural areas in Southeast Asia. In these areas, humans and animals frequently live close together. I’m sure you have noticed all influenza viruses have animal names (swine flu, bird flu…) – that is because the virus jumped from an animal to a person.
The World Heath Organization (WHO) is in charge of collecting flu viruses. They culture a bunch of sick people (nasal swab) to find the new and dominant viruses that season. They get pure cultures of the three worst viruses.
Now the magic begins.
Each virus is combined with a harmless standard lab virus. The result is a new virus that looks like the bad influenza virus on the outside, and like the harmless lab virus on the inside. That is important because the human body generates antibodies to the outside of the virus (it can’t see the inside). Now we have a copy of the virus that can’t make people sick, and grows well in chicken eggs. All this happens at the WHO labs.
Next it’s off to the vaccine manufacturers.
This harmless copy virus is injected into fertilized chicken eggs that are 9 to 12 days old. Three days later there are almost countless copies of the virus in the egg white. The virus is then separated from the egg white. Now it’s time to kill the virus with chemicals as we don’t want anyone being infected by this new virus (even though it is harmless). Now the virus is broken up to get a solution of the surface proteins (those on the outside).
This solution, called antigen, is then diluted to the proper concentration for use.
Next, it’s sterilized and packaged in vials and syringes.
There are hundreds of quality assurance tests done at each step of the process.
So your flu vaccine contains just the proteins from the outside of the original bad virus. It doesn’t have the ability to infect you as there is no living virus in the vaccine.
When you get your flu shot, these proteins (antigens) in the vaccine stimulate your body to make antibodies against this interloper. These antibodies will attach to the original virus and destroy it. In about 9 days you have enough antibodies to fight off an assault by the original virus.
It takes six months from finding a new virus to mass-producing the vaccine. That original virus was found in our spring (the Southern Hemisphere’s fall) and is ready for use by our fall season – just in time for flu season.
Producing the new trivalent (3 viruses) vaccine each year is one of the things the human race does very well; it requires worldwide cooperation to pull it off.
So, when you get your flu shot this year (and do it soon to maximize your protection), appreciate the “magic” that half cc of vaccine represents.