The efficacy of the Pfizer BioNTech vaccine in preventing Covid-19 infections has declined by nearly a third in Israel largely due to the spread of the delta variant, data from the country’s health ministry suggests.

The vaccine had a 64 per cent efficacy rate from early June until early July, the latest figures show, down from 94 per cent a month earlier. The decrease coincides with a period in which the government reversed coronavirus restrictions and the delta variant spread through the country.

But the vaccine is still conferring strong protection against severe symptoms of the virus, with hospitalisation rates remaining low. The ministry’s data shows the vaccine’s efficacy in preventing hospitalisation was 93 per cent from June 6 to July 3, compared to a 98 per cent rate in the previous period.

On Monday, Israel reported the highest rate of new infections since the start of its most recent outbreaks, with the ministry recording 343 new cases over the past 24 hours.

In the past fortnight 90 per cent of new cases have been caused by the delta variant, which is more than twice as contagious as the original strain. Recent data has shown that over half of new cases have been detected in fully vaccinated patients.

After recently reimposing an indoor mask rule for public spaces, Prime Minister Naftali Bennett is scheduled to meet Health Minister Nitzan Horowitz on Monday to discuss the latest outbreak and whether to advise a third booster shot for certain demographics.

Pfizer CEO Albert Bourla has said people will “likely” need a third dose of a Covid-19 vaccine within 12 months of getting fully vaccinated.

Israel may also consider limiting the size of permitted gatherings and reintroducing the “Green Pass” system that limited access to certain spaces to vaccinated people, Ynet news website reported.

Israel’s world-leading coronavirus response has fully vaccinated 57 per cent of the population and 88 per cent of those over 50, who are considered most at risk of serious illness.