Why do we need to get new flu shots each year?
Shots. No one likes them! No one likes getting sick, either. What is it about the flu shot that means I need a new one each year, but I don’t need a shot each year for other diseases?
Bite-Sized Science
When viruses reproduce or make copies of themselves, they can check their work and see how well they made a copy. This is just like how when you are typing something, you check your work and use the backspace when necessary to delete errors. Some viruses are better than others at checking their work. The flu virus in particular is pretty bad at checking its work and correcting mistakes. Accumulation of mistakes can lead to new kinds or strains of flu virus.
These strains can be different enough either during one flu season or year to year that the flu vaccine doesn’t work as well, because it was made to be for a different strain that what you were exposed to. Don’t worry though, because even if you get the flu, you are less likely to get seriously ill from it if you’ve had your shot.
A Closer Look
Accumulation of changes in genetic material, or mutations, ultimately drives evolution. Although the errors themselves happen randomly, if the errors produce a trait that gives an advantage, these get selected for. This is the process of natural selection - organisms that have a survival advantage are more likely to reproduce and pass on their genes.
After many generations, this can lead to the emergence of new species. Keep in mind, evolution happens to species, not individuals, and only after time. There are also other mechanisms that can drive evolution beyond random mutations, but that is the subject of another lesson!
Suggestions for Teaching
Have students research other mechanisms that can cause evolution.
Have students research viruses and determine which ones mutate faster than others.
Have students study the CDC FluView website to ask questions about the current flu season.