A fourth vaccine dose has been approved for most vulnerable Israelis.

The country’s top public health official says they would initially be given to those with weakened immune systems.

”We will continue to track the data on a daily basis,” says Nachman Ash, director-general of the Health Ministry.

”We will see if we need to broaden this recommendation to more of the population.”

The Sheba Medical Center says it would start giving fourth doses to heart transplant patients early Friday.

Israel began trials of the fourth dose at the center earlier in the week, giving them to about 150 medical personnel who had received a booster in August.

Israel was among the first countries to roll out Pfizer’s vaccine a year ago and began administering boosters last summer.

Israel has also just received its first shipment of 20,000 doses of Pfizer pills that treat the worst effects of COVID-19.

It’s among the first countries to get Paxlovid, which can be taken at home to fight off the most severe symptoms.

More shipments are expected as the company ramps up production.