The American Medical Association, American Pharmacists Association and American Society of Health-System Pharmacists are calling for an "immediate end" to prescribing, dispensing or using the deworminig drug ivermectin to treat or prevent COVID-19.

Ivermectin is available in different formulations for both people and animals to treat parasites. It is not approved to treat or prevent COVID-19, nor is there enough evidence to support its use. Though amid a surge in COVID-19 cases in the U.S., internal data from the Centers for Disease Control and Prevention reviewed by ABC News estimates a 19-fold increase of the medicine being distributed during the first week of August, alongside an increase in reported cases of illness related to ivermectin toxicity.

The prescribing and dispensing of ivermectin has increased 24-fold since before the pandemic, according to the medical and pharmaceutical associations, which said in a joint statement they were "alarmed" by an exponential increase in recent months as well.

"[We] are urging physicians, pharmacists, and other prescribers -- trusted healthcare professionals in their communities -- to warn patients against the use of ivermectin outside of FDA-approved indications and guidance, whether intended for use in humans or animals, as well as purchasing ivermectin from online stores," the associations said. "Veterinary forms of this medication are highly concentrated for large animals and pose a significant toxicity risk for humans."

-ABC News' Sony Salzman

Moderna has submitted initial data to the U.S. Food and Drug Administration on its vaccine booster, the pharmaceutical company announced Wednesday.

Its booster candidate would be half the dose (50 micrograms) of the original dosing (two shots of 100 micrograms each).

Federal officials have said they hope to begin administering booster shots for many Americans starting on Sept. 20, with the third shot at least eight months after the second.

The FDA has only authorized booster shots of Pfizer's and Moderna's COVID-19 vaccines for people who are immunocompromised. The Centers for Disease Control and Prevention's independent advisory board also recommended booster shots for those with weakened immune systems.

Pfizer is also seeking authorization for a third dose of its COVID-19 vaccine. The FDA announced Wednesday it will hold a public meeting of its independent advisory committee on Sept. 17 to discuss the application.

-ABC News' Eric Strauss

Even with the delta variant, schools are still safe for children if guidelines are followed, CDC Director Rochelle Walensky said Wednesday at a town hall with the National Parent Teacher Association.

For the most part, Walensky said, "there's more disease happening outside of school than there is happening within a school."

Walensky, a mother of three, said she understands why parents are anxious.

But she added, "What we do know is when we implement the guidance for safe schools -- we implement the masking, the ventilation strategies, the cohorting and the screening strategies -- that we can have our kids be safe."

American Academy of Pediatrics President Dr. Lee Beers said at the town hall that it's still a very small percentage of children who get severely sick. The U.S. saw 200,000 cases among kids in the last week with about 2,000 of them hospitalized, Beers said.

-ABC News' Cheyenne Haslett

With nearly 104,000 hospitalized, U.S. hospitalizations are now at the highest point in more than seven months, according to federal data.

Alabama's ICUs remain 100% full while Georgia's ICUs are over 96% full, federal data show.

Nearly 1,000 COVID-19 deaths are now being reported in the U.S. each day, the highest average in more than five months.

-ABC News' Arielle Mitropoulos

A new study by the U.S. Centers for Disease Control and Prevention estimates that roughly 83% of blood donors in the nation have either been vaccinated against COVID-19 or were previously infected with the virus.

This, however, does not mean that more than 80% of Americans are immune from infection. That's because neither vaccination nor prior infection provides 100% protection -- antibodies are just one part of the overall immune response, and immunity wanes over time. The analysis also may overestimate the portion of people with antibodies because blood donors may be more likely to be vaccinated or have previously been infected.

The study, posted online Tuesday by JAMA Network Open, a monthly open access medical journal published by the American Medical Association, took a snapshot of the presence of antibodies from COVID-19 vaccination or prior infection in about 1.4 million donated blood samples from across the United States. The repeated cross-sectional analysis was conducted each month during July 2020 through May 2021, before delta became the predominant variant of the novel coronavirus in the U.S.

The study shows that the number of blood donors who tested positive for antibodies, indicating either vaccination or prior infection, has gone up over time, from 3.5% in July 2020 to 20.2% for infection-induced antibodies and 83.3% for both infection- and vaccine-induced antibodies in May 2021.

Being vaccinated offers better protection compared to prior infection, and it's recommended that people who have previously contracted COVID-19 should still get inoculated.

-ABC News' Katie Bosland and Sony Salzman