Former Obama administration official Dr. Kavita Patel told CNBC on Monday that she expected a Covid vaccine booster to eventually be approved by U.S. regulators due to new, more transmissible variants of coronavirus.

“With the threat of the Delta variant and possibly other looming variants in the future, it seems inevitable that we will need a booster shot,” Patel said on Squawk Box. “But that trillion dollar question is when? It seems like six months is early.”

The comments from Patel, who now works as a family doctor in Washington, came before Pfizer representatives met with federal health officials on Monday to discuss the possible need for Covid booster vaccinations.

Pfizer recently said it is developing a booster shot to combat the highly transmissible Delta variant. In that announcement, the drug maker cited internal data and a study in Israel showing that six months after vaccination, people experience decreased immunity from Pfizer’s two-dose vaccine as Delta becomes the predominant variant in the country.

The company said a third dose of its existing vaccine could help boost immunity. Over the past few months, executives at Pfizer and its German partner BioNTech have said that people will likely need a third dose of vaccine within a year of being fully vaccinated.

However, shortly after Pfizer’s announcement last week, the Centers for Disease Control and Prevention and the Food and Drug Administration released a joint statement stating that fully vaccinated Americans do not currently need a booster vaccination.

This view is supported by health experts like Dr. Ashish Jha, dean of Brown University’s School of Public Health, shared. Jha told CNBC on Friday that he had “seen no evidence yet that anyone needs a third shot”.

While Patel said the data suggests that all three of the Covid vaccines currently approved in the US – the two-dose Pfizer and Moderna vaccines and the Johnson & Johnson single-dose vaccine – offer “more than enough immunity” To protect against severe hospitalization and death, Pfizer did not criticize Pfizer for working on the booster intake.

“I think what we do know is that, even six months ago, immunity declines over time. The question is, how long? ”Said Patel, who served as policy director for the Bureau of Interstate Affairs and Public Engagement in the Obama administration.

People shouldn’t get a third vaccination now, Patel warned.

“We have seen patients who did this accidentally or even deliberately, and they had even more dramatic side effects than the second shot, so I wouldn’t encourage anyone,” said Patel.

Finally, if a booster is recommended by regulators, people should expect the CDC to make recommendations for specific populations, similar to what happened when the vaccine was initially introduced with a focus on high-risk groups. “It won’t come one, it will all,” she said.

Patel said the conversation about booster shots in the US must take into account the global impact, given the difficult introduction in other parts of the world.

“It won’t help the United States if the rest of the world stays unvaccinated and they have the opportunity to get hundreds of millions of doses because we got a booster,” said Patel.