Booster shots for the coronavirus vaccine will be necessary at some point, but it is too early to tell how often they will be needed, Moderna CEO Stephane Bancel told "Maria Bartiromo’s Wall Street" in an exclusive interview.

"The variant is going to be the big question in terms of boosting," Bancel explained to host Maria Bartiromo. "One thing to think about is natural immunity. When you get infected, you make antibodies or [when] you get vaccinated and make antibodies, over time the level of antibodies going to go down, that is normal and natural. Over time boosts are going to be required, it is too early to know how frequently because we don’t have enough data."

Bartiromo questioned whether the variants should be considered "worrisome".

"We don’t know how the variants will impact efficacy in the long term," Bancel said. "In the short term we are not worried. The B 1.1.7, the [variant] identified in the U.K., which is prominent in the U.S. now, we have seen and published that the level of antibody is similar to an old strain of the virus. We feel very good about this one."


Bancel emphasized that Moderna's two-shot vaccine has "an efficacy north of 90%" and "seems to be doing very well in the real world."

"We feel very confident about a vaccine and continue to advise people [that], given the risk of lung disease, it’s important to get the pandemic under control so we could go back to our normal lives and be with their loved ones."

Turning to the U.S. decision to pause distribution of the Johnson & Johnson vaccine due to the reporting of blood clots in a small number of recipients, Bancel said he has been monitoring vaccine safety "very carefully" since his company's shots received emergency authorization from the Food and Drug Administration (FDA) in December.


"I think the good news, if there is a silver lining, is the American people feel great about the CDC and FDA, and how they take the safety of American citizens very seriously," he said. "I believe and trust the FDA, CDC and the scientists and advisors to do the right thing for the American people."

The CEO also emphasized that booster shots "are going to be really important to keep the country safe and open and we are working very hard. In thirty days, Moderna developed a variant boost for the South African strain. We published data this week showing it works very well in animals, we’ll have human data very soon."