Moderna, Inc. (MRNA) shares plunged 5% in Wednesday's intraday trading session following the company's announcement that it has voluntarily withdrawn its application for a combination flu and COVID-19 vaccine. The biotech firm's decision comes amid increasing regulatory scrutiny and challenges in the vaccine market.

The withdrawal of the Biologics License Application (BLA) for mRNA-1083, Moderna's flu and COVID combination vaccine candidate for adults aged 50 and older, was made in consultation with the U.S. Food and Drug Administration (FDA). Moderna plans to resubmit the application later this year after obtaining efficacy data from an ongoing Phase 3 trial of its experimental seasonal influenza vaccine, mRNA-1010.

This setback for Moderna occurs against a backdrop of broader challenges for vaccine makers. The FDA recently announced it would require new clinical trials for approval of annual COVID-19 boosters for healthy people under 65 years, signaling a more stringent approval process. Additionally, Moderna has been grappling with declining COVID vaccine revenues and investor concerns following the appointment of Robert F. Kennedy Jr., a known vaccine skeptic, as the new secretary of the U.S. Department of Health and Human Services. These factors have contributed to a significant decline in Moderna's stock price, which has fallen over 35% year-to-date.