Biden administration officials said they believe they are just a few weeks off from that second goal. “We will hit 160 million Americans fully vaccinated no later than mid-July,” said Jeff Zients, who has been tasked with coordinating the administration’s COVID response, during a press briefing Tuesday.

Zients added that, instead, there would be a new set of goals: to have 70% of American adults 27 years of age and older at least partially vaccinated by July 4th. To date, 65.4% of adults aged 18 and over have been partially vaccinated and 55.9% have been fully vaccinated, according to the Centers for Disease Control.

The administration’s goals, however, are just that: goals. They aren’t legally binding, and COVID safety efforts have been largely left up to municipalities and states to dictate and enforce. Missing the July 4 goal is unlikely to make much of a practical difference in America’s beach towns and shore cities on Independence Day weekend, as an increasing number of states loosen up mask mandates and social distancing protocols—particularly with businesses aching to take advantage of the first long weekend of the summer. (Although Anheuser-Busch’s big beer giveaway could be put on ice.)

But the inability to reach this milestone after a rapid ramp up of the U.S. immunization campaign underscores the problems health authorities are facing in getting more skeptical groups to get their COVID shots. Vaccination rates have been declining in the South and the Midwest, particularly among younger demographics such as the 18-to-26 year old cohort that Zients said needs some more time to catch up to older groups, as well as teens who qualify.

“Here in the South, particularly in Louisiana, Mississippi, we’re seeing really low vaccination rates,” Peter Hotez, codirector of the Center for Vaccine Development at Texas Children’s Hospital, told CNBC in a recent interview. “And less than 10% of adolescents are vaccinated in many of these Southern states, so we have a real vulnerability here.”

Another reason for concern: The spread of the COVID Delta variant, which is making up an increasing share of new coronavirus cases both in America and across the globe. While early studies suggest vaccines such as Pfizer’s and AstraZeneca’s are solidly effective against this variant, especially in preventing hospitalization and death, other research has indicated it could be more deadly for young people — the precise demographic that’s lagging behind in vaccinations.