Moderna (MRNA) said Friday the Food and Drug Administration has pushed back its pending review of the company's respiratory syncytial virus vaccine to the end of the month due to "administrative constraints."

The FDA informed the company that it won't be able to make a decision on the vaccine, called mRNA-1345, by the previously communicated date of May 12. The agency didn't inform the drugmaker about any issues related to the vaccine's safety, efficacy or quality that would block its approval, according to Moderna.

The drug candidate remains on track to be reviewed by Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices during a meeting on June 26-27. That meeting is necessary before the commercial launch of the product, Moderna said.

"Moderna is very grateful to the FDA for their continued efforts and diligence," President Stephen Hoge said in a statement. "We look forward to helping the agency complete the review of our application, and to the June ACIP meeting."

Moderna said last week in its first-quarter financial report that it expects initial regulatory approvals of its RSV vaccine in the first half and plans to launch it this fall in the US. The candidate is currently in a phase 2/3 clinical trial, with the company seeking to gain authorization for the product's use by adults of over 60 years old.

The firm reiterated its full-year 2024 revenue outlook of roughly $4 billion from its respiratory franchise, with about $300 million in sales in the first half. Chief Financial Officer James Mock told analysts during an earnings call that of the $300 million figure, $100 million is estimated to be generated in the current quarter, according to a Capital IQ transcript.