The development and approval of vaccines involve rigorous testing, clinical trials, and regulatory processes to ensure their safety and efficacy. A universal flu shot, which aims to provide long-lasting protection against multiple strains of the flu, is a complex endeavor and may take time to reach the market.
For the most current and accurate information, I recommend checking with the Centers for Disease Control and Prevention (CDC), the U.S. Food and Drug Administration (FDA), or other reputable health organizations for updates on the progress of universal flu shot development and approval in the United States.