A third shot of the Pfizer-BioNTech vaccine will be given to people in the age group as part of a world first in efforts to slow the spread of the highly contagious Delta variant.

Prime Minister Naftali Bennett, launching the campaign, said President Isaac Herzog would be the first to receive the booster on Friday.

Israel was a world leader in the vaccination rollout, with many seniors getting their shots in December, January and February as they were regarded as the most vulnerable sector of the population.

But since the emergence of the Delta variant, the health ministry has twice reported a drop in the vaccine's efficacy against infection and a slight decrease in its protection against severe disease.

The booster campaign, with shots administered by health maintenance organisations, will effectively turn Israel into a testing ground for a third dose before approval by the US Food and Drug Administration (FDA).

"Findings show that there is a decline in the body's immunity over time. The aim of the supplementary dose is to build it up again, and thus reduce the chances of infection and serious illness significantly," Bennett told a news conference.

"I call on all the seniors who received the second dose, go get the supplementary one," he said.

"My first telephone call, after I finish speaking, will be to the person dearest to me, my mother, so that I can take her to be vaccinated immediately."

Pfizer said on Wednesday it believes people need the additional dose to keep protection against the coronavirus high.

The company said it could apply for US emergency authorisation for booster shots as early as August.

A panel of Israeli vaccination experts advising the health ministry overwhelmingly approved the booster campaign late on Wednesday, Bennett said.

People over 60 who received their second dose of the Pfizer vaccine at least five months ago will be eligible.

Last week, the health ministry estimated the vaccine was only 41 per cent effective at halting symptomatic infections over the past month.

Protection against severe disease remained strong at 91 per cent.

Some experts have criticised the ministry's analysis because of possible bias that could be skewing the data.

Others said Israel should wait a little longer to receive more information about the safety and effectiveness of a third shot.

About 57 per cent of Israel's 9.3 million population has been vaccinated.

About 160 people are hospitalised with severe symptoms and daily new infections have spiked to more than 2000, up from a handful of cases per day a few months ago.

Bennett said his government hoped that stepped-up vaccination efforts would enable Israel to avoid further costly lockdowns.

Meanwhile, a Chinese disease-control official has called for increased testing of employees at the country's ports because of concerns about the coronavirus.

Roadblocks were set up to test drivers after a rash of coronavirus cases traced to a major airport.

It has rattled authorities who thought they had the disease under control.

The 171 new cases of the more contagious Delta variant in the eastern city of Nanjing and surrounding Jiangsu province are modest compared with India and some other countries.

But infections traced to Nanjing Lukou International Airport have spread to at least 10 cities.

Drivers who want to leave Jiangsu need to show a negative coronavirus test taken in the past 48 hours, the provincial transportation department announced on Wednesday.

It said 93 checkpoints were set up on highways.

Nanjing, a city of 9.3 million people northwest of Shanghai, ordered tens of thousands of people to stay home.

It is conducting mass testing while experts hunt for the source of the virus.

China has reported 92,811 confirmed cases and 4363 deaths.

with AP

Australian Associated Press