(CNN) — Increased demand has led CVS and Walgreens to limit purchases of children's pain-relief medicine, the companies confirmed to CNN on Monday. Rite Aid said on Wednesday it's limiting certain online purchases.

Manufacturers of these medications say that they aren't sure when the shortfalls might end and that they're working at full capacity, but some experts say the problem could last into the spring.

CVS is restricting both in-person and online purchases to two children's pain relief products. Walgreens has limited online purchases to six over-the-counter fever reducers per transaction, but it does not have an in-store purchase limit. Rite Aid told CNN it does not have in-store purchasing limits, but limits online purchases of 4-ounce grape-flavored Children's Tylenol to five.

"Due to increased demand and various supplier challenges, over-the-counter pediatric fever reducing products are seeing constraint across the country," Walgreens said in a statement. The limits were put into place "in an effort to help support availability and avoid excess purchases."

CVS also cited increased demand for these items and collaboration with suppliers to ensure continued access. The limits were placed to "ensure equitable access" for all customers, according to a statement from CVS.

Rite Aid said it's experiencing high demand of pediatric and adult over-the-counter medications, and is working with suppliers to meet demand.

The moves come amid a brutal respiratory virus season that continues to strain pediatric hospitals. Young children are particularly vulnerable to RSV, which has hospitalized more than 4 out of every 1,000 children younger than 5 this season, according to data from the US Centers for Disease Control and Prevention.

Weekly RSV hospitalizations have dropped dramatically over the past month — but even with the improvements, hospitalizations are still higher than normal. Flu activity remains high, and Covid-19 is trending up across the country.

The Consumer Healthcare Products Association, which represents manufacturers of over-the-counter medicines, says its members "don't have a timeline" for when supply may catch up with demand.

The association represents three major manufacturers of children's pain and fever medications: Johnson & Johnson, the company that makes Tylenol; Haleon, maker of Advil; and Perrigo, which manufacturers store brands.

Anita Brikman, the association's senior vice president of communications and public affairs, says these manufacturers are running 24/7 to supply more medications to stores.

Sales of kids' medications to treat pain and fever are up 65 percent from this time last year, according to the association.

Brikman said one of the members told the association Tuesday that it had increased the number of units shipped to retailers by 130 percent compared with the same time last year.

Her group is happy that numbers from the CDC suggest that RSV and the flu may have peaked and that infections are starting to come down.

"Right now, we are encouraged by the new figures we're seeing from CDC three weeks in a row where the flu cases are starting to go down. We do know this was the earliest onset of this kind of a peak in more than 10 years. But we also have been talking to our manufacturers, and they're hopeful as we get over the peak that this will that the supply will catch up with the demand," she said.

Others aren't sure the recovery will be that fast.

John Beckner, a pharmacist and senior director of strategic initiatives for the National Community Pharmacists Association, says he's hearing concerns about shortages from many member pharmacies.

"My thought is, we're really not going to see a lessening of this until we get through the crux of the flu season, and that's going to be in early to late spring," Beckner said.

He said pharmacists were doing their best to direct people to stores with supplies of children's medications. They are also compounding liquid acetaminophen and ibuprofen for children in some instances when parents can't find it.

"It's definitely a team effort, and pharmacists are really doing yeoman's work right now to try to help take care of their patients," he said.

In the meantime, the Consumer Healthcare Products Association is asking people to purchase these medicines responsibly rather than stocking up, because hoarding will only further stress limited supplies.

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