What caused the Delta variant?

The Delta variant originally emerged in India in late 2020, and it has spread rapidly to become the dominant global variant. Other variants of concern include the Alpha, Beta and Gamma.

The Delta variant emerged through random mutation. 

Viruses constantly change through mutations, which basically means they accumulate changes in their genetic sequence. Mutations occur randomly. Some mutations make a virus stronger so it spreads more easily and maybe makes people sicker. Other mutations make a virus weaker (these mutations do not help the virus and simply disappear). Several mutations of COVID-19 (what we call variants) have emerged since the beginning of the pandemic. The Delta variant emerged as a random mutation. It has become the dominant variant because it makes the virus much more contagious than the original COVID-19 virus. 

Vaccines did not cause the Delta variant. 

None of the vaccines for COVID-19 contain live virus. So there are no chances of getting COVID from vaccination. In addition, all the variants of concern, including the Delta variant, emerged in 2020. COVID-19 vaccinations did not begin until early 2021, several months after the variant emerged. So, all the variants of concern were already circulating before any vaccination started.

Will there be more SARS-CoV-2 variants?

Because viruses undergo mutations randomly, new variants develop constantly. However, most of these do not become variants of concern. So we are not likely to hear about them.

More information about all the variants of concern and variants of interest can be found in this page by the World Health Organization Tracking SARS-CoV-2 variants

If you want to know more about the Delta variant, check out this video from the CDC

Last update: Sept 10, 2021, 1:00 pm ET

Science review: ERS, GSN