On Monday evening, Dr. Stephen M. Hahn, director of the Food and Drug Administration, and Dr. Peter Marks, the director of the FDA's Center for Biologics Evaluation and Research (CBER), rejected a proposal from the U.S. government's Operation Warp Speed to dilute the current supply of coronavirus vaccines in order to boost supply. During an interview on Sunday, Operation Warp Speed's chief, Dr. Moncef Slaoui, said his task force and Moderna (NASDAQ: MRNA) were in talks with the FDA about implementing the idea. Image source: Getty Images. There may be signs of effectiveness at half the dosage tested in trials leading to Emergency Use Authorization of vaccines from Moderna and Pfizer (NYSE: PFE), but the companies didn't test those dosages specifically. Generally speaking, the immune responses seen in blood samples from people who receive half-sized dosages fall in line with immune responses produced by the authorized dose. While the FDA might be willing to use biomarker data to approve new seasonal flu vaccines, the virus responsible for COVID-19 isn't nearly as well understood. The FDA isn't going to authorize, or even condone, altered dosing of new COVID-19 vaccines without real-world outcome data. This includes suggestions that people injected once don't need to worry about coming back in a few weeks for their booster shot. There were thousands of clinical trial participants who didn't show up for their booster shots, and they generally seem well protected. Since this wasn't a point that Pfizer or Moderna originally set out to prove, though, the FDA must insist that another clinical trial with the proposed dosing schedule be completed first. 10 stocks we like better than Moderna INCWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Moderna INC wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of November 20, 2020 Cory Renauer has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source