FDA To Authorize br Vaccine Booster Shots, for Those With Weak Immune Systems.br Authorization by the U.S. Food and Drug br Administration (FDA) for a third COVID-19 vaccine br shot could happen as soon as Aug. 12.br The emergency expansion applies to both two-dose vaccines administered in the U.S., .br Pfizer and Moderna.br The focus of the decision is for those who br have received organ transplants, .br though the authorization applies to anyone diagnosed with a weakened immune system.br An estimated three percent of Americans br live with the condition.br The Biden administration has prioritized br booster shots for vulnerable Americans.br Once approved by the FDA, br a Centers for Disease Control br and Prevention (CDC) advisory br committee will then br consider its efficacy.br The CDC committee is scheduled br to meet on Aug. 13.br Typically, doctors wait for CDC endorsement br before they act on FDA approval.br Booster shots have already been administered to vulnerable citizens of several European nations.br In addition to the decision about third shots br of the Pfizer and Moderna vaccines.br the FDA is likely to fully approve the br Pfizer vaccine sometime in September.