(NewsNation) — Despite multiple baby formula shipments being flown into the United States from overseas, some parents continue to struggle to find formula on store shelves.

Some doctors say the shortage in the U.S. is not getting worse, but it’s not getting better. Hospitals are running out of samples of formula for parents, and there’s still a concern for babies with specific medical conditions.

According to data from IRI, a market research company, 28.3% of powdered baby formula products were out of stock in U.S. stores this month — up from 23.7% in May.

The Biden administration has taken steps to fix the formula shortage, launching Operation Fly Formula in May to speed up imports from overseas formula producers. The U.S. flew in millions of pounds of formula from Europe.

Yet, a big issue that remains is Abbott Nutrition’s production of baby formula. The company’s Michigan factory, which closed in February over contamination, contributed to the national shortage. Production resumed earlier this month. 

Dr. Mark Corkins, nutrition chair of the American Academy of Pediatrics, said he’s not hopeful things will get better immediately.

“We’ve given out a lot of samples, and what we have is pretty much gone at this point. It’s not like we’re on the manufacturers anytime soon because they’re running out, too,” Corkins said.

He continued: “I would love to say, OK, they’re cleaning up the factory, they’re gonna get production rolling. I’d love to say four weeks, but I don’t think that’s realistic. I think it’s going to be more, at least eight, probably 12. We’ll have to wait and see.”

Recently, the FDA said it would help foreign manufacturers stay on the U.S. market for the long term in an effort to diversify the formula supply here.

FDA Commissioner Robert Califf previously predicted the formula shortage could last until July. He said Tuesday that retail data show that supplies have improved with increases in both U.S. production and imports.

“What you’re going to see is a gradual climbing out of the current situation as more and more formula becomes available,” Califf said.

In the meantime, many parents continue to turn to alternatives to buying baby formula by turning to Facebook groups and ordering online.

The Associated Press contributed to this report.