The United States will miss President Biden’s original goal of getting at least one dose of coronavirus vaccine to 70 percent of adults by July 4, White House coronavirus coordinator Jeff Zients conceded Tuesday.

Zients instead announced a new goal: ensuring that 70 percent of Americans age 27 and up receive at least one shot through the July 4 holiday weekend. Seventy percent of Americans age 30 and up have already received at least one shot, Zients said.

The nation needs “a few extra weeks” to ensure that Americans between ages 18 and 26 are vaccinated at rates similar to older adults, Zients said at a White House news briefing. He added that the United States would miss a second goal laid out by Biden: ensuring that 160 million Americans were fully vaccinated by Independence Day.

“We will hit 160 million Americans fully vaccinated no later than mid-July,” Zients vowed. About 150 million Americans are fully vaccinated, according to The Washington Post’s vaccination tracker.

Johns Hopkins University epidemiologist Gypsyamber D'Souza explains how the U.S. can reach coronavirus herd immunity and what happens if that goal is missed. (Brian Monroe, John Farrell/The Washington Post)

Surgeon General Vivek H. Murthy and infectious-diseases expert Anthony S. Fauci also discussed the administration’s continuing efforts to win over unvaccinated Americans, warning that the virus’s delta variant poses elevated risks.

White House officials’ remarks Tuesday are a formal acknowledgment of what had become clear in recent weeks: The United States had fallen behind Biden’s goal as vaccinations slowed, particularly in the South and Midwest. Health officials have struggled to persuade younger Americans to get vaccinated despite lotteries, gifts and other promotions.

Multiple surveys continue to find that nearly one-third of Americans have no immediate plan to get vaccinated, citing objections such as a belief that the coronavirus threat has been exaggerated or evidence that previously infected people retain some immunity to the virus.

Public health experts say they are concerned that the national statistics can disguise significant disparities, such as the relatively low vaccination rates among Republicans and in communities of color.

“The persistent low rates of covid vaccination in some states and regions is far more worrisome than falling a few percentage points short of an interim national target,” said Jason L. Schwartz, a Yale University health policy professor.

NBC News first reported the White House’s planned announcement.

Biden, who in May announced his target of ensuring that 70 percent of adults had received at least one shot by July 4, has avoided mentioning his goal in recent remarks. Instead, the president and White House officials have touted the significant progress in vaccinations this year and the corresponding downturn in coronavirus cases and deaths. Biden also is planning to host an Independence Day celebration at the White House with about 1,000 military personnel and front-line workers, an event intended to mark the nation’s progress against the virus.

In Florida, where nearly a quarter of residents identify as evangelical, some think the best way to combat vaccine hesitancy is directly through the church. (Drea Cornejo/The Washington Post)

As of Tuesday, about 64 percent of adults had received at least one dose of coronavirus vaccine, according to tracking by The Post, up from about 5 percent when Biden took office in January.

“We are going to have a Fourth of July celebration, which is beyond everyone’s highest expectations,” Zients told reporters, crediting the vaccine rollout.

But the pace of vaccinations has slowed dramatically since mid-April, when more than 3 million doses per day were being administered, according to the seven-day rolling average. About 1.1 million shots a day were administered in the past week. The White House has overseen a flurry of activities and promotions intended to boost shots, including coordinating coupon giveaways and advertisements on video game platforms, but with unclear success.

Projections suggest that no more than 68 percent of adults will have received at least one shot by July 4, and that it may take until August to reach Biden’s original goal.

Public health experts have said the United States needs widespread immunity to prevent a resurgence of covid-19 cases this year, particularly as the virus continues to mutate. Zients and others warned Tuesday that the delta variant has been shown to be highly transmissible, is linked to a spike in hospitalizations overseas and poses a higher risk to younger adults.

White House officials and public health experts dismissed the significance of Biden missing his goal, maintaining that they are more concerned about regional variations in vaccination rates that could lead to a rebound of the virus, and focused on ending the pandemic at home and abroad.

“Our aspirational goal for July Fourth was 70 percent of the adult population receiving at least one dose. But that is not the goal line, nor is it the endgame,” Fauci said at the news briefing, adding that “the ultimate goal” is “crushing the outbreak completely in the United States.”

“We’re not slowing down at all. If anything, we’re speeding up,” Zients said.

Sixteen mostly East and West Coast states, plus D.C., have vaccinated 70 percent of adult residents, and four more states are above 68 percent and will probably reach Biden’s original goal. But other states are lagging behind and are set to miss the milestone. Fewer than 50 percent of adults in Alabama, Louisiana, Mississippi and Wyoming have received at least one shot.

The overall figures can disguise the patchwork nature of the U.S. response, with significant variation in vaccination rates and virus spread among regions and even within states.

For instance, in Lawrence County, Tenn. — a rural county on the southern edge of the state, home to a city billed as the “Crossroads of Dixie” — fewer than 35 percent of adults have received at least one shot of vaccine, according to the Centers for Disease Control and Prevention. But in Davidson County, a largely urban county that surrounds the city of Nashville, more than 60 percent of adults have received at least one shot, the CDC said.

Meanwhile, about 77 percent of adults in New London County, Conn. — which features a mix of rural and urban communities, located in one of the nation’s wealthiest states — have received at least one dose of vaccine, according to the CDC.

Liberal groups have blamed GOP officials for minimizing the threat of coronavirus outbreaks, with some Republican governors dismissing opportunities to encourage their constituents to get vaccinated.

“Taking the COVID-19 vaccine is a personal choice,” Oklahoma Gov. Kevin Stitt (R) wrote on Twitter last month. About 56 percent of adults in Oklahoma have received at least one dose of vaccine.

Biden had met earlier vaccination goals, including ensuring that 100 million shots were delivered in his first 100 days in office. Former Trump administration officials who worked on the Operation Warp Speed initiative to speed vaccine development have said that Biden’s goals matched their own projections.