As COVID-19 spreads around the world, scientists are watching closely for changes to how the virus causes illness. If the virus changes in a way that makes it better at infecting people, spreads faster or causes more severe symptoms, those changes are called variants.
As the virus copies itself to infect more people, tiny changes in its genetic code can happen randomly. These are called mutations. The mutations can make the virus better at infecting people, cause more severe illness or help the virus avoid the immune system. Mutations can also make vaccines less effective or cause medicines used to prevent or treat the virus to stop working.
Currently, the most common COVID-19 variant is omicron, which has many offshoots, called sublineages. Omicron has high infectivity and transmissibility, but seems to cause fewer severe lung symptoms than delta or alpha.
In early 2022, scientists feared that an offshoot of Omicron called BA.2 was becoming less contagious and would fade away. However, in the spring of 2022 it became more common and spread rapidly. It also appears to cause fewer serious symptoms than delta and alpha.
Researchers are concerned that the newer variants could put more pressure on hospitals and lead to more cases, hospitalizations and deaths. So far, however, most people infected with current variants haven’t been severely ill and very few vaccinated people are getting sick from these viruses. Vaccine boosters will continue to be important for protecting against the most dangerous variants.