Israel's largest healthcare provider said Sunday a study of more than half a million fully vaccinated Israelis indicated the Pfizer/BioNTech jab gave 94 percent protection against Covid-19.

Clalit Health Services said that in a groundbreaking project its researchers tested 600,000 subjects who had received the recommended two doses of the US-German Pfizer/BioNTech vaccine and the same number of people who had not been innoculated.

"There was a 94 percent reduction in the rate of symptomatic infection and a 92 percent decrease in the rate of serious illness compared to 600,000 similar (subjects) who were not vaccinated," Clalit said in a Hebrew-language statement.

"Vaccine efficacy is maintained in all age groups, including those aged 70+," it added.

Israel's mass vaccination campaign has seen 3.8 million people receive a first dose, while 2.4 million have also received a second shot. 

The country of nine million people, which is currently easing restrictions imposed during its third nationwide lockdown, is aiming to vaccinate everyone over the age of 16 by the end of March.

"The publication of preliminary results at this stage is intended to emphasise to the unvaccinated population that the vaccine is highly effective and prevents serious morbidity," Clalit said Sunday.

It added that the study covered people who had received the second shot at least seven days before being tested, and would be expanded in future.

"With each additional week that passes, we will be able to make the assessment more accurate." 

Accuracy would improve as subjects are tested after 14 days or more from the second dose, it said.

Israel has so far relied on only the Pfizer/BioNTech vaccine, although it holds a small stock of the vaccine developed by US biotech firm Moderna.

Israel secured plentiful supplies of vaccine from Pfizer after striking a data-sharing deal with the US manufacturer.

The agreement stipulates that the Jewish state, which has one of the world's most sophisticated medical data systems, will share real-time information with Pfizer on the vaccine's impact, including on progress towards herd immunity.

Clalit is the biggest of Israel's four health service providers, which collectively provide healthcare to the entire population.

They are directly responsible for vaccinations and collecting data on their impact.