Millions more vaccinated adults across the U.S. became eligible for a COVID-19 booster shot on Friday. And yet, the vast majority of vaccinated Americans were already eligible -- many just didn't know it.
According to an October survey from the Centers for Disease Control and Prevention, 4 in 10 vaccinated adults were unsure if they qualified for a booster. So far, just 32 million Americans have received a booster, or around 18% of the more than 182 million adults who are fully vaccinated.
In announcing the latest recommendations, public health experts at the Food and Drug Administration and the CDC expressed hope that they would cut through the confusion, simplifying the decision for Americans who are wondering: Do I need a booster shot?
Here's what the experts say.
Should you get a booster?
The question has been hotly debated for months but a larger pro-booster consensus has formed over the last week.
Why? A number of reasons, including rising cases in more than half of U.S. states right before a busy holiday travel season and lower temperatures pushing people indoors.
The FDA and CDC made the updated recommendation on Friday. It expanded booster access to all adults who were vaccinated with Moderna or Pfizer over six months ago, and while the recommendation was stronger for everyone over 50 to go get a boost, it applies to everyone 18 to 49.
For Johnson & Johnson recipients, the recommendation already applied to everyone over 18, anytime two months after their shot.
For experts who have long been loud proponents for booster shots, it was a long time coming.
"Enough is enough. Let's get moving on here," Dr. Anthony Fauci, chief medical adviser to the White House and a leader at the National Institutes of Health, said at an event Wednesday, before the FDA and CDC made the final call.
"There's no doubt that immunity wanes. It wanes in everyone. It's more dangerous in the elderly, but it's across all age groups," Fauci said, citing data from Israel and the U.K., where more people were vaccinated sooner and began to first document waning immunity.
Others, like Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine and co-director of the Texas Children's Hospital Center for Vaccine Development, called the decline "both predicted and predictable."
"And the way you fix it is you give that third immunization," he said.
Both Hotez and Fauci believe the vaccines should be used not just to prevent hospitalizations and death, but also infection -- particularly because of the risk of long-COVID, a concerning side effect of the disease that can include long-term fatigue, brain fog and shortness of breath.
"When I got my third immunization, why was I so eager to do it? Well, of course I didn't want to go to the hospital or ICU, but also I didn't want to get COVID," Hotez said.
"I didn't want to get gray matter brain degeneration and cognitive decline and have a brain scan that looks like somebody 20 years older."
But for those still on the fence, Dr. Anna Durbin, an associate professor at the Johns Hopkins University School of Medicine, laid out risk scenarios to consider.
"It really comes down to your comfort level and just what's going to make you as a person feel safer," Durbin said.
If you're traveling overseas or live in areas of high transmission, if you're elderly or have underlying conditions or are frequently out in the community for work, those are all reasons to get a booster, Durbin said.
For young, healthy people who don't feel at risk, Durbin said to keep an eye on rising cases in your area. Consider getting a booster to help tamp down transmission, but also to protect yourself ahead of a surge, Durbin said.
"If we're gonna see a new wave, it's going to be over the winter months most likely. And if you get boosted now, that's going to provide you really good protection through that period of time," Durbin said.
This advice was echoed by the CDC's advisory panel on Friday, which recommended that Americans over 50 "should" get booster shots if they'd received Pfizer or Moderna six months ago, while 18- to 49-year-olds "may" get a booster -- giving a stronger push for people who are older as cases rise.
That said, don't panic if you can't book an appointment right away -- particularly as demand surges with the new recommendation, experts say.
"I would not view it as an emergency that people need to line up on the day of approval and get their boosters necessarily that weekend," said Dr. Dan Barouch, director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center in Boston.
It's still far more important for unvaccinated people to get vaccinated, Barouch said, particularly ahead of the holidays.
"The most important thing is for everybody who will be celebrating to be vaccinated, if they're eligible to be vaccinated. Now, additional boosts may be useful. But the most important thing is that people be vaccinated primarily," he said.
Why has it been so confusing?
To put it simply: "The reason why there is some confusion is because it has been confusing," said Barouch.
"Guidelines are changing," Barouch said. "And in some cases, the guidelines are changing for good reasons: They're changing because what we're seeing is a changing pandemic."
Last week, a patchwork of booster guidance emerged as governors in over a dozen states called for all adults to get a booster before the federal agencies weighed in.
Hotez commended the states for making the "medically correct" decision and being "more nimble" than the original decision from the CDC and FDA, but acknowledged the schism it created in the public health guidance.
"Not as elegant as you'd like -- to have the states be out front by a week or so, but you know, when you're in the middle of a pandemic, sometimes things don't go smoothly as you'd like," Hotez said.
Some, like Hotez, have always believed boosters would be necessary, even before data started to trickle in on waning immunity, and think confusion could've been avoided if the public was always told to expect a booster.
"It should have been messaged to the American people from the beginning that, by the way, don't be surprised when the call comes out to get a third immunization," he said.
Still, there's a fine line to walk in urging booster shots while also encouraging the most impactful group, unvaccinated people, to get their primary vaccinations, which continue to protect well against hospitalization and death for many months.
"We can give all the booster doses we want and until we get people vaccinated, or they all get infected, we're going to continue to see transmission of COVID," Durbin said.
Should you get a booster shot? Experts say it's time originally appeared on abcnews.go.com