The Biden administration’s COVID-19 booster shot campaign is off to a promising start, with about 1 million Americans signed up to receive a third Pfizer dose at pharmacies in the coming weeks, and adverse reactions to booster shots are rare, according to new Centers for Disease Control and Prevention data released Tuesday.

This week, virus cases, hospitalizations and deaths have decreased nationwide. Biden administration officials said the vaccine race equity gap is closing as white, Black and Hispanic people now have similar inoculation rates. Roughly 75 percent of the currently eligible U.S. population has received at least one dose of the COVID-19 vaccine to date, according to the CDC.

More than 400,000 Americans received booster shots at pharmacies over the weekend, White House COVID-19 response coordinator Jeff Zients said Tuesday during a briefing by administration officials. The Biden administration rolled out its COVID-19 booster shot campaign on Friday, providing the shots to elderly and high-risk adults.

The risk of adverse reactions following a third dose of a Pfizer or Moderna vaccine is low. Among the 22,000 individuals studied in a recent CDC review of booster shots, “no unexpected patterns of adverse reactions were observed,” the agency said.

Immunocompromised individuals who received Pfizer or Moderna mRNA booster shots this year reported side effects similar to those after the second vaccine dose, according to the CDC data released Tuesday. The most common side effects the agency tracked include arm discomfort after the shot, muscle fatigue and headaches. The report focused on the more common, less serious side effects and did not highlight rates of rare but serious side effects such as anaphylaxis.

The durability of immunity from a third shot is not yet known, but Pfizer CEO Albert Bourla said at The Atlantic Festival on Tuesday that he expects protection to last around a year. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, also reiterated at the festival his belief that a proper dose for an mRNA vaccine will eventually include three shots.

Although the shots for the groups authorized Friday to get boosters are available only to Pfizer recipients right now, mix-and-match studies for COVID-19 booster shots are ongoing, Fauci said at the White House briefing, and they will be ready soon.

The data on Moderna as a boost for all three versions of the vaccine is ready now, the data on Johnson & Johnson as a boost will be available within a week and the data on Pfizer as a boost for all three will be ready by mid-October, Fauci said.

Kids’ vaccines

The nation also inched closer to vaccinating kids under 12 years old Tuesday when Pfizer submitted additional data to the Food and Drug Administration about the trial of its COVID-19 vaccine for kids ages 5 to 11. The vaccine maker has not yet applied for a formal emergency authorization for that population but plans to do so in the coming weeks.

It represents a significant first step in the effort to vaccinate young, school-age children, a group that is currently ineligible for a COVID-19 vaccine. Currently, the lifesaving shots are authorized only for people ages 12 and up.

The results that Pfizer announced it submitted Tuesday showed that kids ages 5 to 11 produced a strong immune reaction against COVID-19 with two smaller doses of the COVID-19 vaccine. Instead of receiving the standard vaccine regimen, two 30-microgram shots, children responded to two 10-microgram doses of the vaccine, Pfizer said.

Pfizer expects the FDA to authorize its COVID-19 vaccine for younger kids by the end of October “if everything goes well,” Pfizer board member and former FDA Commissioner Scott Gottlieb said earlier this month. A Pfizer spokesperson confirmed that the company is still on track to meet this deadline.

Pfizer expects to submit data for COVID-19 vaccines for kids who are 2 to 5 years old by the end of the year, Bourla said.

Julie Swann, the head of North Carolina State University’s industrial and systems engineering department who studies health systems and models infectious diseases, said in an interview she foresees challenges in kids’ vaccine uptake. Some of the racial and geographical equity speed bumps that adults experienced in the initial COVID-19 vaccine rollout may be exacerbated for kids.

“If it is not done quickly, then the vaccine will be too late to prevent many infections,” Swann said.

Vaccination rates

Meanwhile, the Biden administration says the COVID-19 vaccine equity gap is closing among U.S. adults.

New data from the nonpartisan Kaiser Family Foundation shows that 70 percent of Black adults, 71 percent of white adults and 73 percent of Hispanic adults have received at least one dose of the COVID-19 vaccine. These numbers are a big improvement from May, when there was a 9-point gap between white and Black vaccination rates.

“The Kaiser data clearly show that our relentless focus on advancing equity and ensuring our response reaches the hardest-hit communities in those most at risk has closed the gaps in racial and ethnic vaccination rates,” Zients said.

One significant divide in vaccination status remains. Republicans are much less likely to be fully vaccinated than Democrats, according to the same Kaiser Family Foundation polling; 90 percent of Democrats have received at least one dose, compared with 58 percent of Republicans.

White House COVID-19 racial equity adviser Marcella Nunez-Smith did not discuss any detailed plans to reach these unvaccinated individuals. But she told reporters at the COVID-19 briefing that the administration would not give up on trying to motivate these people to get the shot.

“It might take a little bit longer, but we are absolutely laser-focused on reaching everyone, making sure people know that vaccines do work safely and effectively. We’re all here as public health professionals and physicians, not as politicians, and that is important to convey to everybody. This is not a political or partisan issue,” Nunez-Smith said.

Lauren Clason contributed to this report.