Why do you get a new flu shot every year?

Answer 1

Viruses mutate very quickly. As they move through a population, passing from individual to individual, they change to bypass the immune system defenses and environmental conditions and sometimes they just make random changes from imperfect replications. Many viruses will be almost completely genetically different from their parent or grandparent viruses.

The flu shot we get each year has been developed to contain the three types of currently active flu viruses determined by epidemiologists to be most likely spreading in the next flu season. These are rarely the same viruses year to year because the prior year's viruses have almost always mutated to new forms before they circle around again the following year.

When you get a flu shot, your body reacts and produces antibodies in the blood that fight off those particular flu viruses for life (in some circumstances, but in others the immunity does lessen over time). The problem is that each flu season brings a slightly (or greatly) changed flu virus that the last year's antibodies are usually not very effective in fighting.

More:

The flu vaccine is made based on what scientists think will be the next year's most active flu viruses. If they waited until the first flu cases, there would not be time to produce all the vaccine needed for millions of people. They study what viruses are circulating in other parts of the world to determine scientifically which are the most likely ones to hit during our next flu season. They make a pretty good forecast analysis.

This is also the reason that there is no cure for the common cold: there are 300-some different types of common cold viruses, and each of those can make slight changes (mutations) that make them unable to be recognized as the same by your immune system. Once you have had one of those, you may not ever catch that exact same cold virus again, but the changes and mutations occur often and quickly in the cold viruses, so it is close to impossible for your body to make new antibodies to defend itself against the newest versions or for your previously made antibodies to be close enough to work on the mutated viruses.

Answer 2

Because we need protection from newly created flu viruses which our past vaccinations were not developed to fight.

Influenza viruses are especially able to easily mutate into new forms and strains. Because of this, there is an almost constant creation of new flu viruses to infect humans, some we are susceptible to and some are not able to make us sick for one reason or another.

Each year in the US, the regular flu vaccine is developed to be able to protect us from the three most common types of flu viruses that are infecting people in other parts of the world at that time, and that are the ones that are expected to spread to the US in the following flu season. Because of the way seasonal flu spreads across the world, those viruses that are infecting people in the Eastern Hemisphere or Southern Hemisphere in the summer will be the most likely ones that will cause flu in the Northern and Western Hemispheres in our upcoming flu seasons in the fall and winter. Often the protection we got from the prior year's flu shot will not be effective against the newly created strains.

Answer 3

It is needed because there are probably something new -here let me explain

Pretend there is a virus that makes you vomit, make your head hurt..

If a person gets those symptoms a new symptom might appear like it makes you depressed or muscles hurt.

that's why they need to come up with new ones every year...

I hope this help you :D

Answer 4

Some change each year. There are different viruses developing all the time. The flu changes each year, so each year a new variation of the vaccination is required and people need to get it. In one sense the vaccination is not being repeated, as the vaccination is slightly different each year.

Answer 5

Because influenza virus change regularly

Answer 6

So your vaccinated against the flu