What Is the Delta Variant?

All viruses develop mutations and variants, and the SARS-CoV-2 virus, which causes COVID-19 infection, is no different. Since the start of the pandemic, multiple variants have developed.

One of these variants, B.1.617.2, also known as the Delta variant, has emerged. Initially discovered in India in December 2020, it has now spread across the globe.

Where Delta Has Spread

After starting in India in 2020, the B.1.617.2 variant became the dominant strain in that country. It quickly began to spread and has been found to infect people in over 130 countries. In addition to being the dominant strain in India, it is also the dominant strain in the United Kingdom.

Spread in the United States 

The Delta variant was first found in the United States in March 2021 and has now been found in all 50 states. The Delta variant is currently the dominant strain in the United States. As of August 7, 2021, the Delta variant was responsible for more than 90% of U.S. COVID-19 infections.

Is the Delta Variant More Contagious?

The Delta variant is more contagious than the original COVID-19 virus—estimated to be at least 60% more contagious than the original strains.

The infectiousness of a virus is measured by an R number, or the number of people an infected person will give the virus to. For example, if the R is 1, an infected person is likely to give it to one other person; an R of 5 means an infected person is likely to transmit it to five other people.

Risk of Reinfection

There is currently limited data on breakthrough infections—or COVID-19 infections in people who have been vaccinated against COVID-19 or who have had COVID-19 infection previously. However, one study of a COVID-19 outbreak in July 2021 showed that of the 469 cases, 74% occurred in fully vaccinated persons. Based on these findings, it's unclear whether the Delta variant will lead to an increase in breakthrough infections.

Is the Delta Variant More Severe?

Research is still ongoing, but in a study in Scotland of people infected with the Delta variant, they experienced a higher rate of hospitalization than those who had been infected with other strains of COVID-19.

Will Vaccines Work Against the Delta Variant?

At this time, it appears that those who have been fully vaccinated against COVID-19 infection should be at reduced risk of becoming infected with the Delta variant.

A study published in The New England Journal of Medicine found the Pfizer/BioNTech and AstraZeneca vaccines to be 88% and 67% effective, respectively, against the Delta variant after two shots. Other current studies (which have yet to be peer-reviewed) suggest one dose of the Moderna vaccine is 72% effective at preventing symptomatic disease caused by the Delta variant and the Johnson and Johnson vaccine is up to 71% effective in preventing hospitalization.

With more studies underway, it's still too soon to know if vaccine boosters will be required in the future.

Are Kids More at Risk for the Delta Variant?

As there are no currently approved vaccines for children younger than 12 years old, kids are at risk of becoming infected with the Delta variant. As it is a more contagious strain, kids will continue to be at risk of catching it. In countries such as the United Kingdom, kids were found to have higher rates of infection.

A Word From Verywell

Experts are worried about the spread of the B.1.617.2 variant throughout the United States. As this variant is more contagious, it has the potential to infect many people.

Getting a vaccine against COVID-19 is the best way to protect yourself against this and other strains of the virus. Check with a healthcare provider to be sure the vaccine is safe for you to get. Increasing vaccination rates in the United States and around the world is the best way to decrease the spread of COVID-19.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.