The White House announced last month that booster shots would become available for Americans starting on September 20 following data suggesting waning efficacy of the initial doses.
The announcement was pending approval from regulators, though, and it appears the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention's (CDC) advisory committee may not be able to determine the safety and effectiveness of the third shots by the targeted rollout date.
This has left local health officials in limbo, wanting to be prepared in case the shots do receive approval, but unsure if they will be offered starting Monday.
'We don't want to be unprepared,' Lori Tremmel Freeman, chief executive officer of the National Association of County and City Health Officials, told CNN. The plan laid out by federal officials in August was to offer third vaccine shots to anyone who received the Pfizer-BioNTech or Moderna jabs - the two most commonly used in the U.S.
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Americans would be eligible for the third shot eight months after having received their second.
Those plans have since gone awry, with regulators notifying White House officials they might not be able to approve the vaccine booster by September 20.
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Some have also doubted the need for the third vaccine shots.
Earlier this week, 18 FDA officials wrote a report opposing the roll out of boosters, arguing the current science does not support the need for more shots. Other scientists and health experts claim that despite an increase in breakthrough cases, because the vaccine still is effective at preventing hospitalizations and deaths, more shots are not needed at this time.
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'No one's going to get boosters until the FDA says they're approved, until the CDC advisory committee makes a recommendation. What we want to do though is be ready as soon as that comes,' Ron Klain, White House chief of staff, relayed to CNN earlier this month.
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'A hundred percent we will wait for FDA approval, we will wait for CDC approval.'
Once approval does occur, more than five million Americans will suddenly become eligible to receive the next shot of the vaccine.
Health officials are working to ensure they have the capability to handle a potential surge in vaccine demand.
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'We have been hearing from local health departments, without any confirmed information coming their way, they are beginning to assess who on the ground will have the capacity to do boosters, who will remain as a provider of vaccines and who is pulling out -- so that we have a better understanding of how the community will be served and by whom,' Freeman told CNN.
'There's just a lot of confusion about this.'
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