ROCHESTER, N.Y. — ​The delta variant of COVID-19 was first detected in the U.S. back in March and is now the most prevalent strain of the virus.

Following the Centers for Disease Control and Prevention (CDC) update that vaccinated people should be masking up again in some situations, doctors at Rochester Regional Health say the vaccine still protects against serious illness, but for those who are vaccinated who get infected, also known as a breakthrough case, the levels of the virus in their system is significantly higher than other strains, which means they are more likely to infect others.

“The risk if you’re vaccinated to spread it to somebody else is really low, but it’s not low enough with the delta to say that it’s OK that the risk is high enough now that delta is on the scene,” Dr. Emil Lesho said.

Doctors say it’s still vitally important to get vaccinated, as studies show all current vaccines prevent against getting seriously ill from any COVID variant.

The CDC says vaccinated people should start wearing masks again indoors in high transmission areas.