The Food and Drug Administration announced extended expiration dates for some EpiPens Tuesday to help families that might've had limited access due to a shortage.

The extension is based on “stability data” provided to the FDA that showed the product remained stable, “retaining its strength, quality and purity for up to 24 months when stored according to its labeled storage conditions,” Theresa Eisenman, a spokesperson for the FDA said in an email.

Generally, the EpiPen shelf life is 20 months, but the expansion allows for an additional four months of use. The extended expiration dates apply to EpiPen 0.3 mg Auto-Injectors and the authorized generic, but do not apply to EpiPen Jr.

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For a full list of EpiPen use numbers with expanded expiration dates, check here.

The EpiPen is manufactured by Meridian Medical Technologies, a subsidiary of Pfizer. According to a joint statement from Pfizer and Mylan, the distributor of EpiPen, the extension of expiration dates is meant to address patients’ access, “particularly during the back-to-school season as demand increases.”

“Currently, supplies will vary from pharmacy to pharmacy, and we cannot guarantee that product will be available at all pharmacies,” the statement said, in part.

The shortage is due to manufacturing delays, according to information from the FDA, which was first posted in May 2018.

You can view the full statement from Mylan and Pfizer here.