At least 1.5 million Americans received a booster shot of the Covid-19 vaccine from Moderna or Johnson & Johnson in the first five days after U.S. regulators approved the additional doses, a White House official said Wednesday.

“Our booster program has got off to a very good start,” Jeff Zients, White House Coronavirus Response Coordinator, told reporters during a virtual press conference. He said the government is working with states, pharmacies, and other agencies to get boosters quickly to tens of millions of eligible Americans.

The Centers for Disease Control and Prevention on Thursday approved booster shots of Moderna and J&J Covid vaccines for millions of Americans.

Maryland National Guard specialist James Truong (L) administered Jan.

Chip Somodevilla | Getty Images

The CDC approved the administration of the Moderna booster to elderly and vulnerable adults six months after completing their first series of vaccinations, in line with the sales plan for Pfizer and BioNTechs boosters. It has also released J & J’s boosters for adults who received their first vaccination at least two months ago.

Zients said Wednesday that at least 15 million Americans have received an extra dose of an approved Covid vaccine since health officials released third shots of Pfizer or Moderna vaccines to people with compromised immune systems in August.

While the Biden government is still working to convince hesitant adults to get their first Covid vaccine shots, it is also preparing to hand out doses to younger age groups, he said.

U.S. health officials are expected to approve a smaller dose of Pfizer’s Covid vaccine for children ages 5-11 as early as next week.

States have placed their first orders for the children’s cans, Zients said Wednesday, and millions of cans will be distributed by the US government after federal regulators give approval.

Approximately 28 million children would be eligible for Pfizer’s vaccine pending approval from the Food and Drug Administration and the CDC, he said.