CNN  — 

As Covid-19 cases continue to rise and the Omicron variant sweeps the world, some nations are rolling out fourth doses of coronavirus vaccine for the most vulnerable people.

Israeli Prime Minister Naftali Bennett’s office announced this week that adults 60 and older, medical workers and people with suppressed immune systems could receive a fourth dose if at least four months have passed since their third dose.

On Thursday, Germany’s health minister Karl Lauterbach said that a fourth dose will be needed to maintain protection against the Omicron variant, though the country has not yet initiated a rollout of fourth doses.

Meanwhile in the United States, it’s too early to be discussing a potential fourth dose of coronavirus vaccine for most people, Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said Wednesday.

“I think it’s too premature to be talking about a fourth dose,” Fauci told Michael Wallace and Steve Scott of WCBS Newsradio 880.

“One of the things that we’re going to be following very carefully is what the durability of the protection is following the third dose of an mRNA vaccine,” Fauci said. Moderna and Pfizer/BioNTech are mRNA vaccines.

“If the protection is much more durable than the two-dose, non-boosted group, then we may go a significant period of time without requiring a fourth dose,” Fauci said. “So, I do think it’s premature – at least on the part of the United States – to be talking about a fourth dose.”

Once data are available on fourth doses, the US Centers for Disease Control and Prevention will examine and consider whether there might be a need for them nationally – but for now, third doses appear to be providing “durable protection,” CDC Director Dr. Rochelle Walensky told CNN’s John Berman on Tuesday.

“If there’s science and when there’s science that demonstrates that that is necessary, we will certainly be reviewing that,” Walensky said.

“Right now, we’re working to make sure that our vaccinated people get a booster,” she said. “We have many vaccines where two shots – primary series – and a booster gives some durable protection. So, while I think it’s an important question to evaluate, it may very well be that we have some added protection by this booster shot right now.”