The company clinched a hard-won victory after the US Food and Drug Administration approved the use of its mRNA flu vaccine in adults aged 50 and up. Because they use a synthetic genetic code, mRNA vaccines can be updated quickly to combat variant strains, unlike traditional vaccines, which take weeks to grow in eggs or cell cultures. The FDA’s sign-off was based on a trial involving more than 40,000 adults 50 and up that found the shot 26.6% more effective than a standard flu vaccine. Seasonal vaccine sales rely on advance commercial contracting with healthcare providers, pharmacies and distributors, which is why Wall Street doesn’t think Moderna will make any meaningful mFlusiva sales until the 2027-28 flu season. Meanwhile, the European Union approved its first-of-its-kind COVID and flu combination vaccine in April.