Do I need to get tested for COVID-19 if I’m vaccinated?

Yes, if you’ve been around someone who has COVID-19.

Read: Should vaccinated people mask up with COVID-19 cases rising?

The latest guidance from the U.S. Centers for Disease Control and Prevention says people who are fully vaccinated should get tested three to five days after a potential exposure, even if they don’t have symptoms.

That change comes two months after the agency eased its initial testing guidance. In May, the CDC said vaccinated people face very little risk of serious illness and don’t need to be tested in most cases, even if exposed to someone who was sick. The thinking was that vaccinated people also weren’t likely to spread it to others.

But the agency says it’s reversing that guidance because of the more contagious delta variant, which now accounts for most COVID-19 infections.

The COVID-19 vaccines are still very good at protecting people from getting seriously ill, but the CDC says new data shows vaccinated people infected with the delta variant could spread it to others.

Read:Bhutan fully vaccinates 90% of eligible adults within a week

Doctors, nurses and other health care workers should consult with their employers, some of whom may require routine testing for their staff. People working in prisons and homeless shelters are also generally subject to stepped-up testing requirements.

U.S. citizens returning from abroad still have to present a negative COVID-19 test before boarding their flights home, regardless of their vaccination status. Anyone who tests positive for COVID-19 should still isolate for 10 days, the CDC says.