AV on Health: Vaccine Boosters

The Pfizer vaccine has received full authorization from the federal Food and Drug Administration. The CDC and other governmental health organizations are strongly recommending those fully vaccinated with the Pfizer or Moderna vaccine receive a booster shot. The Biden administration is making preparations to roll out the additional shots beginning September 20, 2021. When will Moderna get full authorization? Why is full authorization so important to so many? Why is it necessary to get an additional shot? Who is eligible? Is it safe? Will it prevent the spread of the virus? Were the first two shots not strong enough?