Nurse practitioner Tabe Mase gave Biden a dose of a vaccine against COVID-19 at Christiana Hospital, in Newark, Delaware on Monday.

“Today, I received the COVID-19 vaccine. To the scientists and researchers who worked tirelessly to make this possible — thank you. We owe you an awful lot. And to the American people — know there is nothing to worry about. When the vaccine is available, I urge you to take it,” Biden tweeted.

On Monday, Army Gen. Gustave F. Perna, Operation Warp Speed chief operating officer said that the COVID-19 vaccine distribution had a strong week last week, with 2.9-million doses initially coming from pharmaceutical company Pfizer.

OWS officials expect about 7.9 million Moderna and Pfizer vaccines to be distributed this week.

“Drug-maker Moderna has 5.9-million doses going to 3,400 locations, and 2.1-million Pfizer vaccines are going to 1,000 locations today and tomorrow,” Perna said.

He added that the vaccines will continue to be ordered on a repetitive basis.