Dr. Anthony Fauci said the single-dose Johnson & Johnson vaccine should've been a two-shot vaccine from the beginning. The nation's top infectious diseases expert was speaking at ABC's "This Week" on Sunday.
"What the advisers to the FDA felt is that, given the data that they saw, very likely this should have been a two-dose vaccine to begin with," Fauci said.
The J&J vaccine was launched as a one-dose regimen. The FDA granted EUA for J&J's vaccine in February 2021, 70 days after Pfizer and Moderna.
The FDA advisory committee unanimously approved booster shots for the vaccine Friday for all J&J recipients 18 years and older â as early as two months after the first dose.
"So I think that's a very good thing. And I think it's very favorable for those who have received the J&J vaccine," he said. "I don't see that as a problem at all," Fauci added.
On Wednesday, the National Institutes of Health released a study that says, "If you got the Johnson & Johnson vaccine as your first Covid-19 shot, a booster dose of either the Moderna or Pfizer-BioNTech vaccine apparently could produce a stronger immune response than a second dose of J&J's vaccine."
Responding to the question based on that study which has not yet been peer reviewed, Fauci said that the FDA and the CDC will give booster flexibility based on the recipient's health situation, such as whether the individual is susceptible to known adverse reactions linked to mRNA vaccines, such as myocarditis (aka heart inflammation).
Pfizer and Moderna's Covid-19 vaccines are both mRNA vaccines, while the J&J vaccine is a viral vector vaccine, reported HuffPost.
"For example, a woman of child-bearing age who would have almost no issues at all with a possible adverse event of myocarditis ... that person might want to opt for that approach," he said of receiving one of the mRNA vaccines after the initial J&J shot.
"If you're a young man who does have that very, very rare risk of getting myocarditis, you might want to take the J&J route," Fauci added.
As the FDA has recommended J&J boosters for a wider group of Americans, many are waiting for the Moderna and Pfizer boosters to be expanded to the general public. Pfizer and Moderna boosters are limited to those aged 65 and up, aged 18 to 64 with either underlying health conditions, or whose job that puts them at high risk of exposure to Covid-19.