WASHINGTON -- U.S. President Joe Biden said Wednesday he will make COVID-19 booster shots available to all American adults beginning next month, as his administration warned that vaccines are showing a declining effectiveness against infection.
The move comes as scientists and health experts grapple with how to beat back the surging Delta variant of the coronavirus, and follows extensive debate over whether a third injection of the Pfizer-BioNTech and Moderna vaccines would be appropriate.
Stressing this was "no time to let our guard down," Biden urged every American 18 and older to get a booster eight months after becoming fully vaccinated.
"This will boost your immune response, it will increase your protection from COVID-19, and it's the best way to protect ourselves from new variants that could arise," Biden said in an address from the White House.
"It will make you safer, and for longer -- and it will help us end the pandemic faster."
According to the plan, which is still pending a final evaluation by the Food and Drug Administration, the boosters would become available beginning the week of Sept. 20.
Biden also unveiled a new facet in the push to increase vaccination rates: mandating nursing homes to require all workers be fully vaccinated as a condition for receiving federal funding for social safety net programs like Medicare.
The president highlighted how vaccination rates of the nation's 1.3 million nursing home workers "significantly trail" the rest of the country.
Earlier in the day, the nation's top health authorities described how "waning immunity" after receiving vaccinations and the strength of the widespread Delta variant were necessitating a booster for most Americans.
"We are concerned that this pattern of decline we are seeing will continue in the months ahead, which could lead to reduced protection against severe disease, hospitalization, and death," U.S. Surgeon General Vivek Murthy said in a video press conference.
Murthy and other members of the White House COVID-19 response team said that while vaccines remain remarkably effective, the best way to shore up protection is through a booster.
They said they also anticipate booster shots will be needed eventually for people who received the Johnson & Johnson vaccine, which rolled out in March.
More than 620,000 people have died in the United States from COVID-19, with case numbers increasing sharply in recent months due to the spread of the Delta variant.
Just over 50% of Americans are fully vaccinated, as the country's mass immunization program faces resistance in politically conservative regions in the South and Midwest and among some racial minorities.
Anthony Fauci, the country's leading infectious disease expert, pointed to studies showing significant drops in vaccine protection over time.
For instance, figures released by the Mayo Clinic showed that the effectiveness against the Delta variant slid from 76 to 42% with Pfizer's vaccine, and from 86 to 76% with Moderna's.
But a booster dose would increase the antibody levels in COVID-19 vaccines tenfold, according to Fauci.
"Higher levels of antibodies are associated with higher levels of vaccine efficacy," he told reporters.
Biden also addressed the concerns recently expressed by foreign leaders that a massive booster effort for Americans would come at the expense of billions of people worldwide who have yet to receive any coronavirus vaccine.
"I disagree," the president said. "We can take care of America and help the world at the same time."
While the government gears up to administer some 100 million booster shots in the United States, it will be donating more than 200 million additional doses to other countries.
Overall, the U.S. plans to donate more than 600 million vaccines worldwide.