The Delta variant of the coronavirus, known as B.1.617.2, is raising some concerns among health experts. Why? Because it seems to spread more easily and be harder to detect. But there’s good news too: So far, COVID-19 vaccines work well against this strain of the virus. Here’s what to know to help keep yourself and your loved ones safe.

Q: What is the Delta variant?

A: Many viruses mutate over time. The Delta variant is a new mutation of the coronavirus that was first found in India. It has now spread to more than 60 countries. In some, it has become the dominant strain. Around 60% of new coronavirus cases in the United Kingdom are caused by this strain. In the United States, about 6% of new cases are associated with the Delta variant. But that number has been rising.

Q: Why is it a potential problem?

A: The Centers for Disease Control and Prevention calls Delta a “variant of concern.” That means it has some qualities that require close monitoring. In Delta’s case:

• It appears to be more contagious.
• It may be harder to detect, even in people who are vaccinated.
• It may cause more severe illness.
• It may be resistant to some treatments.
• In some places, it is affecting more young people.

Q: Why is it important to be fully vaccinated?

A: If you are fully vaccinated, you are less likely to get severely ill—from Delta or other variants. For two-dose vaccines, like Pfizer’s and Moderna’s, that second shot is crucial. It may offer significantly more protection against Delta than the first shot alone.

In the U.K., one shot of the Pfizer vaccine was shown to be only 33% effective against Delta. But two doses were 88% effective.

The bottom line: To prevent Delta from taking over in the U.S., it’s important for everyone to be fully vaccinated as soon as they can be.