For much of this year Israel has been hailed as a resounding Covid-19 success story. It rolled out one of the world’s fastest vaccination drives, reopened its economy and jettisoned all remaining lockdown restrictions last month.

Now rising infection rates, driven by the more infectious Delta variant, have forced the Israeli government to reintroduce restrictions for the first time since January.

While hospitalisation rates remain low, Israel has chosen a cautious approach. Israelis once again have to wear masks inside and on public transport. Testing sites have been reopened. Multiple other restrictions, including stricter quarantine for travellers and greater testing of children, are expected to be introduced. Israel may even bring back the “green pass”, which allowed greater freedom for vaccinated people.

“We are not waiting to protect the health of Israeli citizens. It must be understood, the Delta variant is running amok around the world at a much higher rate than all of the previous variants,” Israeli prime minister Naftali Bennett said on Sunday.

Israel spearheaded one of the world’s fastest vaccination drives after it secured plentiful supplies from Pfizer in return for sharing data on the jab’s impact. But cases have ticked up since Israel lifted all remaining Covid restrictions on June 1, with many experts blaming the highly transmissible Delta variant brought into Israel by returning travellers.

Passengers at Israel’s Ben Gurion airport

After weeks of single-digit daily infection rates, the number of new cases has ballooned to more than 400 per day this week. As of Wednesday, the country had more than 3,345 active cases — almost triple that of the previous week — though the health ministry said only 46 were considered seriously ill. And while the number of infections is increasing, its coronavirus rate — at 25 new cases per 100,000 people every seven days — is still far lower than the UK, which has a rate of 267. Cyprus, the EU country with the most new infections, has a seven-day rate of 424.

Israeli hospitals’ Covid wards remain largely empty, with health experts urging vigilance and calm.

“[Israel’s] numbers are rising, and will continue to rise. We’re definitely at the start of a fourth wave, which could be bigger in terms of overall infection numbers,” said Professor Gili Regev-Yochay, director of the Infection Prevention and Control Unit at Sheba Medical Center. “But the numbers of seriously ill are much lower [than previous waves] and it won’t collapse the health system. We have to be alert, not panicked or hysterical.”

Log scale line chart showing new confirmed cases of Covid-19 in Israel, UK, Portugal, Spain, Cyprus and US

A preliminary study compiled by the health ministry this week indicated that the BioNTech/Pfizer vaccine was still 93 per cent effective against serious illness and hospitalisation, but only 64 per cent effective at preventing infection.

“According to the Israeli data, there is a potential decrease in vaccine effectiveness against infection and mild disease with respect to Delta, and strong preliminary signals to that effect,” said Dr Ran Balicer, a senior official at the Clalit health organisation and chair of the Israeli government’s national Covid advisory committee. But Balicer and other health experts cautioned that the study was based on preliminary and highly localised infection numbers, and faced several methodological challenges.

Studies in other countries have also documented a drop in efficacy for the Pfizer jab against the Delta variant versus earlier strains, though less severe. Public Health England in May found the vaccine provided 88 per cent protection against symptomatic infection with Delta, and 93 per cent against the Alpha variant first identified in Kent, England.

People without masks at Carmel Market in Tel Aviv earlier this year

More than 5m of Israel’s 9m citizens have been fully vaccinated with the Pfizer vaccine. Since the recent uptick in case numbers, a fresh effort has been launched to inoculate the estimated 1.2m remaining teenagers over the age of 12 and unvaccinated adults. While parents were initially reluctant, over the past week 150,000 teenagers have received the jab, including Prime Minister Bennett’s 14-year-old daughter.

“The single most important factor for the long-term control of disease spread is increasing the number of vaccinated,” said Dr Balicer. “It decreases the severe cases and heightens the ‘vaccine wall’ against disease dissemination.”

With the new Covid guidelines, the government is going a step further, although the chances of a new nationwide lockdown — similar to the previous three the country imposed over the past 18 months — was “very, very low,” according to Regev-Yochay.

“These aren’t draconian measures . . . that hurt the economy. Moderation and proportionality are key,” Dr Balicer said.

The Israeli public, for its part, appears frustrated by the new restrictions, offering a glimpse of the challenges that may lie ahead for governments that find they need to reinstate restrictions.

The mask mandate introduced last week has been met with only partial success. Avi, 50, a freelance boat captain, forgot his mask one recent weekday as he shopped at a central Tel Aviv supermarket. “I was on buses earlier in the day and then now in the supermarket — no one said anything to me,” he said. “I’m a law-abiding citizen, but [once] we got used to going with [masks], they stopped it. Now we have to get used to it again. They’re driving us crazy.”

Matan, 52, the owner of a nearby café, was even more scathing about the new measures. “They only need to check one thing: how many seriously ill there are. It’s not going up anywhere. If it was a bad flu, would they shut down the entire country? No,” he said. “It’s a joke. The new [Bennett] government, they seem like good people, but they and the media don’t have to run a business.”

Officials hope that the public will ultimately understand the need for these new initial steps — and that further restrictions won’t be necessary.

“No one knows what will be the effect if we just let the disease run out of control. We don’t want to have to make a severe U-turn down the line,” said Dr Balicer.