Albert Bourla, CEO of drugmaker Pfizer, has tested positive for Covid-19 and is “feeling well,” he said in a tweet Saturday.

Bourla said he does not have any symptoms.

“While we’ve made great progress, the virus is still with us,” he said.

The CEO said he did not get the updated Covid-19 booster shot yet because he is waiting for three months after his previous Covid-19 infection. He tested positive for Covid-19 in August.

The US Centers for Disease Control and Prevention recommends that people who have recently recovered from a Covid-19 infection wait to get boosted at least until the illness has passed and a person is no longer contagious. The CDC says a person “may consider delaying your vaccine by 3 months from when your symptoms started.”

Getting infected can act like a booster and studies have shown that people have a relatively low risk of getting sick again for about three months after they recover.

People may not want to wait as long as three months if Covid-19 levels are high in the community or they have a reduced immune function, CNN has reported.

The CDC signed off on the updated booster shots from Pfizer and Moderna on September 1.

Pfizer/BioNTech’s updated vaccine is a 30-microgram dose authorized for people 12 and older. Moderna’s updated vaccine is a 50-microgram dose authorized for people 18 and older.