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
Where should I go for trusted and up-to-date information on Covid-19 vaccines?
The Centers for Disease Control and Prevention (CDC) has great information on the Covid-19 vaccines, including a FAQ page. Another CDC resource will direct you to state Department of Health websites. Those sites will help you determine when you can get the vaccine in your area. This website ( will also be continually updated to provide trusted information on all Covid-19-related matters, including vaccines. You can find an interactive state map with links to state…
I'm young and healthy. Should I get vaccinated?
While not considered to be at high risk for severe complications from Covid-19, serious cases do occur among younger, healthier people. The Centers for Disease Control and Prevention (CDC) also warns of the potential long-term health effects of Covid-19 infection, even for those who experienced mild illness. In addition, young people can still be carriers of the virus and contribute to community spread without ever having symptoms. Therefore, you should still get vaccinated when one becomes…
Is a monoclonal antibody treatment the same as a vaccine? If not, what's the difference?
Monoclonal antibody treatments are not the same as vaccines. Monoclonal antibodies are medicines that directly deliver man-made antibodies against a virus to your body to help fight off infection. To treat Covid-19, the FDA has approved two monoclonal antibody treatments for emergency use -- bamlanivimab and the casirivimab and imdevimab antibody cocktail. These treatments are given to patients through an IV and attack the natural spike protein found on the surface of the Covid-19 virus. The…