Some people are hesitant to get the flu shot this year because they may have gotten one before, and still caught the flu. What they should say is they caught one of the flues.
There are multiple strains of flu viruses circulating that are constantly evolving.
They are grouped into four types; A, B, C and D. Types A and B cause annual epidemics. Type C does not… while type D primarily affects cattle.
Type B appears to only affect humans, however, type A viruses can circulate among humans and animals. Only type A viruses are known to have caused global pandemics.
There are three ways a virus can spread. The first is transmission directly from one member of a species to a member of another species. For example, if a chicken gave a flu virus to a human.
Then, there's adaptation, when a virus goes from one species to another species, and it adapts the virus and spreads it to a third species. For example, if a chicken could give a flu virus to a pig, which then changes it and passes onto a human.
There's also genetic re-assortment, when gene segments from two different types of influenza viruses combine in the cells of the species to make a new type of flu.
This means flu viruses are constantly changing, and have many different strains.
Each year, The World Health Organization (WHO) tries to figure out which influenza strains are most likely to cause epidemics. They have five labs across the world. Those labs analyze samples so the WHO can try to make the most beneficial vaccine that year. It means the shot you get at the pharmacy or doctor’s office protects you against the influenza viruses research suggests will be most common in the upcoming season.
Sure, there’s an off chance you may catch some other type of flu but at least you’re protected from these ones.
Because flu viruses are constantly changing, so are flu vaccines – getting updated each season to give you the best protection. That’s why it’s important to get vaccinated every year.