How do viruses mutate?

Viruses change all the time. That's because they copy themselves to reproduce. Think of our cells as having their own xerox machines, which the virus takes over for its own purposes. When a virus makes a copy, sometimes a random change can occur in the copy's DNA -- the double spiral-shaped molecule which acts as a manual telling our bodies how to develop and function. If enough of these changes happen over time, a new variation or strain of a virus can emerge. 

Mutations happen in two main ways. In the first, small copying errors in the virus lead to changes in the virus' surface proteins, which sit on the outside of the virus. These proteins look to attach to your cells (much like boats seeking to tie to a dock). These changes result in more closely related virus variations, like the new Covid-19 variants.

In the other way, two variations infect the same cell in a person's body and combine to form a new or "novel" virus. This often happens when a variation that only infects animals comes into contact with a human variation. This version of mutation could have created the novel coronavirus which causes Covid-19.

Our immune systems respond differently to different virus variations, and so do vaccines.

Related Questions
Are children eligible to receive the Covid-19 vaccine?
The FDA has authorized the Pfizer-BioNTech and Moderna vaccines for use in children older than 6 months based on strong safety and effectiveness data. Learn more. To find a vaccine near you, you can search, text your ZIP code to 438829, or call 1-800-232-0233.  You can also schedule an appointment with your child’s physician or healthcare provider. Alternatively, you can visit your local pharmacy's website to see if vaccination walk-ins or appointments are…
Can I mix Covid vaccines and/or booster shots?
The FDA has authorized mixing booster doses of the Pfizer-BioNTech, Moderna, and Johnson & Johnson vaccines. Following the completion of primary (two shots for Pfizer and Moderna and one shot for J&J) vaccination, eligible individuals may choose to use the same or a different available Covid-19 vaccine as their booster dose.
Who is eligible for a booster shot?
The FDA has authorized booster shots for tens of millions of people who previously received two Pfizer-BioNTech or Moderna doses, including: Seniors ages 65 and older Adults ages 18+ who have underlying medical conditions that put them at increased risk of the virus Adults ages 18+ in long-term care facilities, such as nursing homes or assisted living People at increased risk of the virus due to their working or living situations -- including first responders, teachers and school…
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.