Moderna says it is working on an omicron-specific booster shot, but whether we will all need a fourth dose will come down to how the next few months go.
"We need to be careful to try to stay ahead of the virus, and not behind the virus," said Stephane Bancel.
Though he says those who recently got a booster shot likely have strong antibodies against COVID-19, an Israeli study found those who are given a fourth dose see antibodies increase five times over.
Moderna says its own tests of a generic booster show antibodies increasing by a multiple of 37.
FILE - Nurse administers a COVID-19 vaccine. (Scott Olson/Getty Images)
"Time will tell on this," said Tampa General Hospital Chief Medical Officer Dr. Peggy Duggan. "The third shot, we have just started seeing the benefit from that. We just need to follow people and see when that immunity wanes."
Right now, 36% of Americans who got two doses of either Pfizer or Moderna have also had booster shots, according to the CDC.
This week, those with weakened immune systems can get a fourth shot under rules that considered their primary doses three shots instead of two.
Whether we will all need it depends on data related to breakthrough cases with omicron and what happens to antibody counts over time, says Duggan.
"That's what we have to look at. How risky is the disease? What is the volume of it? But it would surprise me if after three shots we are all done," she said.
But University of South Florida virologist Dr. Michael Teng says there may be such a thing as too much of a good thing. Three doses are definitely better than two, but he says the science is still out on number four.
"You are starting to see diminishing returns with the fourth dose," he said. "There is going to be a limit where you are not going to be able to keep stimulating your immune system."
Israel has made the fourth dose available to anyone over 60 who got their third shot four months ago; 100,000 Israelis have taken advantage so far.
Moderna says its omicron-specific booster might be ready by fall.