The head of Pfizer said on Monday he had tested positive for Covid-19.
Albert Bourla said he was experiencing mild symptoms, and was feeling well while isolating.
He has started a course of Paxlovid, an antiviral drug developed by Pfizer.
The 60-year-old said he had received four doses of the Covid-19 vaccine developed by his pharmaceutical company in partnership with German biotechnology firm BioNTech.
“I would like to inform the public that I have tested positive for Covid-19,” Mr Bourla said in a statement issued by Pfizer.
“I am grateful to have received four doses of the Pfizer-BioNTech vaccine and I am feeling well while experiencing very mild symptoms.
“I have started a course of Paxlovid, I am isolating in place, as well as following all public health precautions.
“We have come so far in the past two years in our efforts to battle this disease that I am confident that I will have a speedy recovery.
“I am incredibly grateful for the tireless efforts of my Pfizer colleagues who worked to make vaccines and treatments available for me and people around the world.”
Mr Bourla also shared news of his positive test on Twitter.
The Pfizer-BioNTech vaccine has been widely used across the globe to help limit the spread of the virus.
US President Joe Biden recently tested positive for the virus twice.
Mr Biden, 79, emerged from isolation at the White House on July 27 after testing positive for the first time on July 21.
He tested positive again on July 30 in what Dr O'Connor described as a “rebound” case which occurs in a small percentage of people who take the antiviral drug Paxlovid.
The illness prevented Mr Biden from travelling and attending public events, although he appeared at meetings online.