Updated Covid Booster shots expected to be rolled out in September by Biden Administration.

The Biden administration plans to offer updated Covid booster shots in September, an administration official confirmed to NBC News on Friday.

The new vaccines will be reformulated to perform better against the now dominant, and extremely contagious, omicron subvariant BA.5, and also the BA.4 subvariant.

Both Pfizer and Moderna say they’ll have the retooled boosters ready by the fall, and the federal government has purchased millions of doses to allocate to the public, but it’s not enough to inoculate every American.

News of the fall rollout of updated boosters was first reported by The New York Times.

BA.4 and BA.5 — considered the most contagious forms of the virus to date — made up more than 90% of all new Covid cases in the United States for the week ending July 23, according to the Centers for Disease Control and Prevention.

Health officials have raced to address the aggressive subvariants, with the U.S. Food and Drug Administration last month recommending that vaccine manufacturers update their shots to target BA.4 and BA.5.

On Friday, the Department of Health and Human Services and the Department of Defense announced an agreement to purchase 66 million doses of Moderna’s bivalent Covid vaccine booster.

The federal government also recently purchased 105 million bivalent Covid vaccine booster doses from Pfizer-BioNTech for potential use later this year.

Once those bivalent vaccine boosters are authorized by the FDA and the CDC, the first deliveries by both manufacturers will be received in the early fall, Health and Human Services said in a news release.

Together, Moderna and Pfizer will provide 171 million bivalent vaccine booster doses for the fall and beyond, if authorized and recommended — but that’s not enough for each American to get a dose, according to the release.

Health and Human Services said that both the Moderna and the Pfizer agreements include options to provide 300 million doses from each company, for a total of 600 million doses, “but these options can only be exercised with additional funding from Congress.”

The department stressed in the release that existing Covid vaccines “remain the single most important tool in preventing serious illness, hospitalization, and death.” Given the threat the BA.5 subvariant poses, it’s vital that Americans “stay up to date with their Covid-19 vaccinations.”

“We must stay vigilant in our fight against COVID-19 and continue to expand Americans’ access to the best vaccines and treatments,” Health and Human Services Secretary Xavier Becerra said in the release. “As we look to the fall and winter, we’re doing just that—ensuring Americans have the tools they need to stay safe and help keep our nation moving forward.”

Currently, only Americans over the age of 50, or those over the age of 12 with certain immune deficiencies, are eligible for second booster doses. Of those over age 50 who received their first booster, only about 30% have received their second, according to CDC data.