New COVID-19 boosters aimed at fighting currently circulating variants of the coronavirus will be widely available this week, U.S. health officials said on Tuesday, adding that the vaccine is moving closer to an annual jab, as with flu shots.

By the end of this week, 90% of Americans will live within five miles (8 km) of sites carrying updated vaccines, U.S. health secretary Xavier Becerra said at a White House briefing.

They will remain available at no cost, White House COVID-19 Response Coordinator Ashish Jha told reporters.

Officials said people could get the new boosters this fall and winter alongside their regular annual flu shots.

The redesigned boosters, green-lighted by U.S. health regulatory agencies last week, aim to tackle the BA.5 and BA.4 sub-lineages of the virus's Omicron variant.

The so-called bivalent vaccines also still target the original version of the virus.

They represent a shift in U.S. response strategy, said Jha.

"For the last two years, this virus has continued evolving while our vaccines have stayed the same, but now we have a vaccine that matches the dominant strain out there," he said. "For the first time since December of 2020, these vaccines are vaccines that have caught up with the virus."

U.S. Centers for Disease Control and Prevention (CDC) Director Rochelle Walensky said even with the seven-day average of COVID hospitalizations down 14% to 4,500 per day, annual shots could save thousands of lives.

"Modeling projections show that an uptake of updated COVID-19 vaccine doses similar to an annual flu vaccine coverage early this fall could prevent as many as 100,000 hospitalizations and 9,000 deaths, and save billions of dollars in direct medical costs," she said.

Omicron subvariants BA.5 and BA.4, which are targeted by the retooled boosters, account for over 88% and 11% of circulating viruses, respectively, she said.

Top U.S. infectious disease expert Dr. Anthony Fauci said unless a dramatically different variant emerges, "we likely are moving towards a path with a vaccination cadence similar to the annual influenza vaccine."

"However," he added" "some particularly vulnerable groups may continue to need more frequent vaccination against COVID-19."

Regulators have so far backed COVID-19 boosters for those aged 12 and older from Pfizer/BioNTech and 18 and older for Moderna's.

Jha told reporters at the briefing it was not yet clear when they could be approved for younger children, but that there may be an update on the timing later in the fall.

He said that because Congress has not provided enough COVID response funding, the updated vaccines are available for free at the cost of pulling other resources like personal protective equipment and at-home tests, leaving the national stockpile ill-equipped to deal with another surge in cases.

Becerra said there was enough vaccine supply for the fall campaign, but the future is uncertain.

"We may have the vaccines today for folks for this fall vaccine effort. We don't know what's coming next. We don't know what the next generation of vaccines will look like if we don't have the resources to continue that research going," he said.

His department last week said the government's vaccine and antiviral treatment supply would run out over the next year, meaning they would start being sold commercially sooner than previously expected rather than doled out free.

The government also cited a lack of funding when it said Americans would no longer be able to order free at-home COVID tests from its COVIDTests.gov website.