Booster shots aimed at increasing resistance to COVID-19 were expected to begin as early as next week, but state Department of Health officials are still waiting for federal agencies to give final approval to the shots and provide guidance on how to administer them, leaving expectant residents in limbo.

A third dose of the Pfizer-BioNTech and Moderna vaccines was expected to be available for residents starting the week of Sept. 20 if eight months had passed since their second dose. That would apply to about 17,000 Hawaii residents, according to data from the Centers for Disease Control and Prevention.

Ultimately, the state is expected to have to dole out extra shots in the coming months to over 1 million residents who have been vaccinated this year. Individuals receiving the Johnson & Johnson shot, which was administered beginning in March, are also expected to be eligible for another dose.

But President Joe Biden’s announcement last month about the booster shots was conditioned on approval from the U.S. Food and Drug Administration, which is still pending and a subject of hot debate among scientists.

On Monday an international group of scientists, including some from the FDA, published a review that concluded that the available data on coronavirus vaccines doesn’t yet provide credible evidence in support of boosters for the general population.

The paper, published in The Lancet, said booster shots ultimately may be needed in the general population due to waning immunity or new variants of the virus, but warned that there could be health risks if the boosters are introduced too soon or too frequently.

The authors of the paper included two FDA scientists who last month announced they were leaving the agency, in part because they disagreed with Biden’s push for boosters before their agency could review the evidence and make recommendations, according to national news outlets.

Biden’s announcement was also controversial because much of the world population still hasn’t had access to the lifesaving vaccines, while the American supply is robust.

An FDA committee is expected to meet Friday to evaluate the booster shots. Typically, a CDC advisory committee then issues recommendations, according to local health officials.

The dust-up has left the state Department of Health unsure of what to prepare for. For instance, officials don’t know whether the FDA will approve the same eight-month interval between the second and third shots that Biden had previously announced, said Brooks Baehr, a spokesman for the Health Department.

“We also don’t know if, for example, the CDC may recommend booster shots for certain age groups before others. There are lots of unknowns and that is why we’ve got to wait,” said Baehr by email.

While the state undertook a major effort to set up vaccination sites throughout the state when the shots first became available and were highly coveted, Baehr said the state isn’t anticipating having to do that again. There are now more than 230 sites throughout the state offering the vaccines, as well as more than 200 pop-up vaccination events scheduled for September.

The state is also not anticipating having to contend with a limited supply of vaccines, as in the early days of the rollout when the size of shipments was closely watched.

As of Tuesday, Baehr said, the state had 188,000 vaccine doses on hand, which doesn’t include the doses supplied by federal agencies. The state has the capacity to administer more than 60,000 doses a week without opening additional vaccination sites.

Hospital officials are also getting ready to offer booster shots, but they too are waiting on the federal guidance.

Hawaii Pacific Health is poised to make booster shots available immediately at its on-site vaccine clinics at Kapiolani Medical Center for Women & Children on Oahu and Wilcox Medical Center on Kauai, as well as its mobile vaccine clinics, said Kristen Bonilla, a spokeswoman for the hospital system. She said Hawaii Pacific Health also might open additional vaccine sites.

Beginning last month, the state has been administering a third dose of the Pfizer- BioNTech and Moderna vaccines to residents who are immunocompromised and whose bodies may have not mounted an adequate immune response to the virus.

So far, 10,790 residents have received a third dose of one of the vaccines, according to state data.

The administration of a new layer to the state’s vaccination program comes as local health officials are still grappling with a major surge in COVID-19 cases resulting from the highly contagious delta variant. Over the past two months, they’ve had to hustle to set up more testing sites, find extra medical oxygen supplies, import more than 600 nurses and other health care professionals, and set up triage centers.

While the rapid rise in cases appears to have plateaued, health officials warn that Hawaii’s case counts and hospitalization numbers are still too high. On Tuesday the Department of Health reported 423 new coronavirus infections, including 338 new cases on Oahu, 23 on Maui, 41 on Hawaii island, 14 on Kauai, five on Molokai and two Hawaii residents diagnosed outside the state. Hospitalizations were down slightly to 357, according to state data.