When a virus infects a person, it copies itself over and over. Each copy can have different genetic changes, which are called mutations. Mutations can make the virus better at infecting people or spread faster. They can also make people sicker. Mutations can also change how well a vaccine or medicine that prevents or treats COVID-19 works.
When scientists track the COVID-19 virus in people, they see lots of changes. Some of these changes are important. They can cause more serious illness and death. They can also affect how quickly the virus spreads or how easily it is caught and diagnosed. Scientists call these major offshoots variants. There are five main COVID-19 variants that have caused most cases: alpha, beta, delta, gamma and omicron.
Each of these can have many offshoots, which are called sublineages. Viruses that are close in lineage have a lot of shared changes and tend to grow or die out. The most dangerous viruses are called Variants of Concern (VOCs) or Variants of Interest (VOIs).
The most common mutations in the COVID-19 genome occur in the spike protein, which helps the virus enter cells and escape from the body’s immune response. The more mutations in the spike protein, the more likely a virus is to escape the immune system and spread. The vaccine and antiviral medicines used to treat COVID-19 also target the spike protein. Research on the structure, infection mechanism and immunology of the virus is pointing to ways that vaccines and drugs may become more effective against these dangerous variants.