Why Doesn't The Flu Vaccine Last Forever?

By Victoria Simpson on April 6 2020 in Answer

The flu vaccine prevents you and others from contracting different types of influenza. Photo by CDC on Unsplash
The flu vaccine prevents you and others from contracting different types of influenza. Photo by CDC on Unsplash
  • Only influenza A is known to cause global flu pandemics.
  • Influenza D infects cows.
  • There are four types of influenza and they can mutate readily.

Each fall, often sometime in October, doctors, medical clinics and drug stores in North America and elsewhere start advertising the flu shot. Depending on where you live, it could be offered for free or for anywhere between about $15 and $70, depending on your age and the type of flu shot you are getting. 

Some vaccines you only need to get once in your life. Why do you need to get the flu shot every year? There is a simple explanation to this question: because the specific strain of flu in circulation changes from one season to the next. Flu strains also mutate, and so what was mild one year could be a more dangerous strain, the next. 

Types of the Flu

There are four main types of influenza viruses logically named A, B, C, and D. Here’s a bit about each. 

Influenza A

Influenza A has the capability to cause a pandemic, so that is why you must get vaccinated every year. Photo by CDC on Unsplash

Influenza A and B are the two nasty viruses that cause the seasonal flu epidemics each year in North America. Influenza A viruses are the only ones thought to be able to produce a global pandemic, like the one that happened in 2009 with the H1N1 virus. 

Amazingly, there are potentially as many as 198 different subtype combinations of influenza A, but so far, only 131 have been found in nature. Subtypes occur in influenza A because there are two different proteins that can be present on its surface. Influenza A can be either influenza A(H1N1) or influenza A(H3N2). 

Within these two types of proteins, there are further variations, leading to the potential for 198 different subtypes of influenza A. As you can imagine, it is impossible to produce a vaccine that can cover all these potential combos and types of influenza A, hence there is a need for a different flu shot to be produced each season, in order to get it right.

Influenza B

As mentioned above, influenza B also causes yearly epidemics. Influenza B, like A, has two different initial types as well. They are called lineages, instead of subtypes, and they are influenza B (Victoria) and influenza B (Yamagata) respectively. Influenza B is not so strong as A, however, and is not thought to cause pandemics. 

Influenza C 

Influenza type C generally causes a mild infection, and as such, it is not thought that it is responsible for any yearly epidemics nor global flu pandemics. You may get the sniffles and some sore muscles with this one, but you will soon be back on your feet. 

Influenza D

If you have never heard of influenza D there is a good reason for it. It is because humans do not get it. This type of flu generally infects cows, leaving humans off the hook. 

What Flu Vaccine is Needed Yearly?

The process to develop a new flu vaccine each year is a long one. According to the CDC, there are over 100 national influenza centers in over 100 countries worldwide that conduct year-round surveillance for the flu, every year. These centers receive and test thousands of flu samples from patients. These results are then sent to the World Health Organization (WHO), and officials there make recommendations as to what should be in that year’s flu shot. Each country then makes its own decision about which viruses to include in their flu shot that year. 

There are some restrictions. The vaccines developed need to be similar to the flu viruses predicted by the WHO to circulate in any given year. In addition, what they are made of also depends on whether or not there is a good vaccine virus available to use. Sometimes there is not a good one available, and so the shot is not as effective. 

Do You Really Need It?

Flu vaccines help you develop antibodies. Photo by CDC on Unsplash

When you get your flu shot, your body receives a bit of the virus that has been deactivated, so that it will not make you sick. The vaccine will, however, make your body develop antibodies in response to it. This provides your body with extra power should you fall sick with the real flu. 

Yes, the flu shot is not perfect. For many, however, getting their shot is something they do every year. The flu shot is not guaranteed to keep you from falling sick with the flu in any given year, but studies have shown that it does reduce your risk of falling seriously sick from about 40% to 60%, which is significant. The shot can also significantly reduce a child’s chances of dying from the flu, which is important. In short, the flu shot does not harm you, and it could actually save your life, and it is definitely something to consider getting. 

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