Despite around 60% of Americans being fully vaccinated against COVID-19, health officials warn that hospitalizations are rising as the Delta variant continues to surge, with immunity within vaccinated people declining.

Public-health officials have displayed apprehension regarding this upcoming winter season and the potential of another surge in cases, though those who are unvaccinated are still at greater risk, being 11 times more likely to die from the virus.

"What we're starting to see now is an uptick in hospitalizations among people who've been vaccinated but not boosted," said Dr. Anthony Fauci, the chief medical advisor to President Joe Biden.

On Friday, the Food and Drug Administration authorized all adults to get booster shots of the Pfizer BioNTech and Moderna vaccines. They were initially available only to specific groups that were more at risk to severe symptoms of COVID-19.

"Authorizing the use of a single booster dose of either the Moderna or Pfizer-BioNTech vaccine for individuals 18 years of age and older helps to provide continued protection against COVID-19,” FDA commissioner Janet Woodcock said.

Fauci also emphasized the efficacy of the booster shot.

"The effect of boost is very, very favorable to preventing people from getting infected," he said.

Analysis shows that the booster shot is recommended for nearly 100 million people.

The Pfizer COVID-19 vaccine was approved by the FDA on Oct. 29 for children in the 5-11 age group, almost a year after it was made available for adults.