The US Food and Drug Administration on Monday fully approved the Pfizer-BioNTech Covid vaccine, a move that triggered a new wave of vaccine mandates as the Delta variant batters the country.
Around 52 percent of the American population is fully vaccinated, but health authorities have hit a wall of vaccine hesitant people, impeding the national campaign.
"This is a pivotal moment for our country in the fight against the pandemic," acting FDA Commissioner Janet Woodcock told reporters in a call.
"This FDA approval should give added confidence that this vaccine is safe and effective. If you're not vaccinated yet, now is the time," tweeted President Joe Biden.
Pfizer's vaccine, which will now be marketed under its brand name Comirnaty, is the first to receive full approval.
More than 200 million Pfizer shots have already been administered under an emergency use authorization (EUA) that was granted on December 11, 2020.
The decision to fully approve it among people aged 16 and up was based on updated data from the drug's clinical trial involving more than 40,000 people, which found the vaccine 91 percent effective in preventing Covid.
"Overall, approximately 12,000 recipients have been followed for at least six months," the FDA said in its statement.
Most commonly reported side effects are mild and include pain and swelling at the injection site as well as headache, chills and fever.
The FDA is continuing to investigate safety data regarding the more concerning condition myocarditis (heart inflammation), particularly within seven days after the second dose.
The highest risk has been detected in boys aged 12 through 17, with available data suggesting most individuals recover but some require intensive care.
Military, NYC announce mandates
The US military said shortly after the announcement that it would mandate the vaccine, and a slew of private businesses and universities are expected to follow.
New York City also said it would require all its department of education employees to receive at least one dose of vaccine by September 27, without the option for regular testing instead.
The vaccine remains available under emergency use authorization to children aged 12 to 15, but because it has now been fully approved, physicians may prescribe it to children under 12 if they believe it will be beneficial.
Woodcock however recommended against so called "off-label" use in younger children until clinical trials report their data, which is expected later this year.
"We need to get the information and data on usage in younger children — they are not just small adults," she said, emphasizing that knowing the correct dosage for this group was key.
Boost for vaccination campaign
Amesh Adalja of the Johns Hopkins University Center for Health Security hailed the development as "good news" that may sway people still on the fence.
"One of the talking points of the anti-vaccine movement which has falsely claimed that this was an 'experimental vaccine' has been removed," he told AFP.
"Hopefully now you'll see people who said that they were waiting for full approval line up to get vaccinated."
A recent survey by the Kaiser Family Foundation found 30 percent of adults said full approval would make them more likely to get vaccinated.
Experts had been urging full approval for months.
But FDA scientist Peter Marks told reporters the agency had to first review hundreds of thousands of pages of patient data, monitor clinical trial sites to ensure they were collecting information accurately, and inspect manufacturing facilities.
Approval comes as the ultra-contagious Delta variant pummels the country, with around 80,000 Americans hospitalized with Covid and more than 700 dying every day.
The hardest hit regions include southern states Florida, Alabama, Mississippi, and Louisiana.
The number of people rolling up their sleeves for a shot has risen in these states in recent weeks, but the national rate is still well below its peak from spring.
Some 628,000 people have died from coronavirus infection in the United States, making it officially the hardest hit country in the world — though experts say it is possible that India may in fact hold the record.
Vaccines are less effective against the Delta variant than they were against previous strains, particularly against infection, making the goal of high population level vaccination critical.
The Biden administration announced last week plans to make a booster shot immediately available for immunocompromised individuals and recommended all vaccinated people get a third shot eight months after their second.