TEL AVIV (AFP, NYTIMES) - Israel on Monday (July 12) began administering a third shot of the Pfizer-BioNTech coronavirus vaccine to patients with compromised immune systems, as cases in the country rise, the health ministry said.

Those immediately eligible for a third shot include people who have had heart, lung and kidney transplants and some cancer patients.

"There is accumulating evidence that patients with immunosuppression do not develop an adequate antibody response after two doses of the vaccines," a health ministry statement said.

It added that the decision to give a third dose was spurred by the rising daily case tally.

Israel's initial vaccine roll-out of the Pfizer-BioNTech jab was among the world's fastest, and it succeeded in bringing confirmed daily cases down to single digits last month.

With more than 85 per cent of its adult population fully inoculated, Israel had removed all its pandemic containment restrictions, restoring indoor dining and removing caps on large gatherings.

But the emergence of the Delta variant - first identified in India in April - has led to a surge in transmission, with several hundred new infections now recorded daily.

Experts have said there are clear signs the vaccine is less effective in preventing mild illness against the Delta variant.

Sheba Medical Centre near Tel Aviv began giving third Pfizer shots to dozens of heart transplant recipients Monday afternoon, an hour after receiving a green light from the Ministry of Health.

"It's really urgent to do it now," Dr Galia Rahav, the head of the Infectious Disease Unit and Laboratories at the Sheba Medical Centre, said in a video statement, citing the rise of the Delta variant.

The hospital said it would be testing and tracking the recipients of the third shot for research purposes.

Health care providers in France have been giving a third dose of a two-dose vaccine to people with certain immune conditions since April.

The number of organ transplant recipients who had antibodies increased to 68 per cent four weeks after the third dose, up from 40 per cent after the second dose, one team of French researchers recently reported.

In the United States, there has been no concerted effort by federal agencies or vaccine manufacturers to test this approach.