More people are currently hospitalized with COVID-19 in Iowa than at any other point this year so far, according to weekly data released by the Iowa Department of Public Health on Wednesday.

The data shows that there are now 638 people hospitalized with the disease statewide, up from 578 last week. Although the figure is nowhere near Iowa's peak of more than 1,500 in mid-November last year, it's the highest number of COVID-19 hospitalizations that the Hawkeye State has recorded since December.

Of those currently hospitalized, 161 patients were in intensive care, according to the data.

More than 65% of Iowa residents ages 18 and over are fully vaccinated against COVID-19, data shows.

The U.S. Food and Drug Administration has authorized a third booster dose of Pfizer's COVID-19 vaccine for people who are 65 and older or at high risk of severe COVID-19, the agency announced Wednesday.

The dose is authorized to be administered at least six months after the second shot. High-risk recipients must be at least 18 years old.

The announcement comes days after a similar recommendation from FDA advisers.

The U.S. Centers for Disease Control and Prevention's advisory board is scheduled to vote on booster recommendations Thursday.

The Florida Department of Health issued an emergency rule Wednesday that lets parents choose whether to quarantine their children if they are deemed a close contact of someone who tested positive for COVID-19.

In such cases, parents can let their children "attend school, school-sponsored activities, or be on school property, without restrictions or disparate treatment, so long as the student remains asymptomatic," the emergency rule stated.

The move is the state's latest to empower parents when it comes to coronavirus measures in schools. In July, Gov. Ron DeSantis issued an executive order giving parents the choice of whether to send their kids to school with masks, setting off an intense back-and-forth between the state and districts that mandated masks in the weeks since.

DeSantis touted the new "symptoms-based approach" during a press briefing Wednesday.

"Quarantining healthy students is incredibly damaging to their educational advancement," he said. "It's also incredibly disruptive for families all throughout the state of Florida."

At least one superintendent in Florida has spoken out against the new quarantine rule.

"I find it ironic that the new state rule begins with the phrase 'Because of an increase in COVID-19 infections, largely due to the spread of the COVID-19 delta variant,'" Carlee Simon, superintendent of Alachua County Public Schools, said in a statement posted to Twitter Wednesday.

"In fact, this rule is likely to promote the spread of COVID-19 by preventing schools from implementing the common-sense masking and quarantine policies recommended by the vast majority of health care professionals, including those here in Alachua County," she added.

-ABC News' Will McDuffie

At the ongoing CDC advisory committee meeting, Dr. Anne Hause presented preliminary data showing a low rate of serious adverse events among the over 2 million people who have already received booster doses.

Nearly all adverse events reported were not serious (95%) for both Pfizer and Moderna third doses, according to data collected from the national reporting system, which is not a formal, controlled study.

Dr. Sara Oliver of the CDC called booster effectiveness and safety data “reassuring," adding, "but many unknowns remain.

Committee member Dr. Sarah Long urged her colleagues to stay focused on how well vaccines specifically prevent hospitalizations and severe illness.

“I would just encourage us not to lump infection and hospitalization,” Long said. “I don’t think there’s any hope that vaccines such as the ones we have will prevent infection, after the first maybe couple weeks that you have those extraordinary immediate responses."

-ABC News' Sasha Pezenik

The nation’s largest union of registered nurses pushed back against the U.S. Centers for Disease Control and Prevention advisory panel's vote on COVID-19 booster shots, calling not including front-line workers like nurses in its recommendations "unconscionable."

National Nurses United is urging CDC Director Rochelle Walensky to bypass what the advisory panel, ACIP, recommended and add nurses and other health care workers to the list of eligible booster recipients.  

"Nurses and other health care workers were among the first to be vaccinated because of their high risk of exposure to the virus," Deborah Burger, the union's president, said in a statement. "Why leave them out of booster shots?"

“It is unconscionable that ACIP would not vote to keep us safer from death, severe Covid, and long Covid,” Burger continued. “We must do everything possible to ensure that the health of our nurses and other health care workers will not be put even more at risk."

ACIP voted Thursday to recommend a third Pfizer dose for people aged 65 and older, as well as those as young as 18 if they have an underlying medical condition.

In its authorization Wednesday, the Food and Drug Administration did agree to make the shots available to front-line workers. But ACIP said there was not yet enough data to support providing booster shots automatically to young people because of their jobs.

-ABC News' Sasha Pezenik