Pfizer and Moderna have released studies that show their COVID vaccines lose potency over time, and questions are mounting about Americans needing a third dose as a booster.
Pfizer says its data shows the effectiveness of its vaccine drops by six percent every two months after the second dose, not because of the Delta variant, but because of the vaccine's efficacy.
It's one reason why medical experts say that so-called "breakthrough" cases are happening across the country among those fully vaccinated.
"What we've seen is increases in cases and breakthrough cases as time goes on, just because of a waning immunity, and this is why this booster question is coming into play right now," said Dr. John Brownstein, an epidemiologist at Boston's Children's Hospital.
Pfizer is now recommending that folks 16 years and older get a booster shot six months after getting the second dose.
"Big picture: boosting is important, boosting is necessary," said Angela Hwang, president of Pfizer's Biopharmaceuticals Group.
It all comes as the Delta variant surges. On Wednesday 2,000 deaths were reported and while some of those may have been due to data backlogs, it's still the highest single day in nearly seven months.
Hospitals in Idaho are now rationing care and it's a similar situation in Alaska and Montana.
The FDA meets on Friday to review Pfizer's clinical trials and other research to determine whether there's enough data to recommend that Americans need that extra shot in the arm at this time.
"There's no medical downside because the safety profiles of these vaccines are incredibly good," Dr. Brownstein contended. "At the same time, we want to wait for the FDA and then CDC to really learn the best timing and dosage that they recommend."
However, some at the FDA say it might not be needed for everyone.
"This data is persuasive," said Dr. Carlos del Rio with the Emory University School of Medicine. "It is quite persuasive to me that it will be wise to give boosters to people over the age of 60. I am not convinced that this data is persuasive enough to give boosters to everybody."
Meanwhile, Moderna is releasing its own studies also showing breakthrough cases among those fully vaccinated a year ago versus those who recently got the jab.
Moderna's president is also making the case for booster vaccines, though he says their inoculation appears be the strongest against the Delta variant among the three vaccines being used in the U.S.
"It's not the kind of thing that you want to miss by six months, you'd rather be a little too early than a little too late because ultimately, lives are at stake," said Stephen Hoge, president of Moderna Therapeutics.
Unlike Pfizer, Moderna is asking the FDA to allow its boosters to be a 50 microgram dose, half the dosage of the first two shots.
A month after the Biden administration recommended that adults who got either Pfizer or Moderna start getting boosters this month, there's been a debate on whether there's sufficient data to warrant the extra shot.
Health experts from around the world, including two FDA vaccine leaders, wrote in The Lancet Medical Journal this week that vaccine boosters are not necessary right now based on the current data and pushed back against White House plans to rollout booster shots for everyone.
Meanwhile, religious objections to vaccines were once used sparingly but are now becoming much more widely invoked against getting COVID vaccines.
And that's likely to increase following President Biden's vaccine mandates. The administration acknowledges that more people will use the exceptions.
Union officials expect there will be many requests for exemptions among federal employees.