Israel told its citizens on Friday they must again wear masks indoors, 10 days after being allowed to ditch them, amid a sustained surge in coronavirus infections attributed to the highly contagious Delta variant.
The mask requirement had been one of only a few social curbs remaining as Israel's rapid vaccination drive kept cases down.
But daily infections more than quadrupled this week to 138 after outbreaks attributed to the Delta variant at two schools, prompting officials to tighten some restrictions again and urge parents to have children between 12 and 15 vaccinated.
The Health Ministry reimposed the mask requirement for all indoor settings except the home, and said it was also recommending masks be worn at large outdoor gatherings, specifically mentioning gay pride events taking place around Israel this weekend.
The annual Tel Aviv Pride Parade, which was cancelled last year due to the pandemic, drew massive crowds Friday.
Some 55% of Israel's 9.3 million population have received both doses of the Pfizer-BioNTech vaccine.
Eligibility was extended to 12- to 15-year-olds last month, but take-up in that age group has been low.
In April, coronavirus czar Prof. Nachman Ash said Israel could achieve "herd immunity" when 75% of its population were either vaccinated or naturally immune after having contracted COVID-19.
But on Thursday, allowing for the higher contagiousness of the Delta variant, he put that figure at "at least 80%".
Following two major virus outbreaks that were detected in Binyamina and Modi'in last week, Ash said that additional hotspots had cropped up across the country in recent days, including in Kfar Saba, Ramle and Herzliya.
"Our shared mission is to rein in the outbreak and reduce morbidity to a bare minimum," Ash said.
"I call on whoever should to go get tested. Whoever came into contact with a confirmed [coronavirus patient], it is important to get tested, regardless of whether you are vaccinated or not."
Ash also urged Israelis returning from abroad to self-isolate upon their arrival and reconsider non-essential travel outside of the country's borders in order to prevent the spread of new coronavirus variants in the population.
"Adhering to isolation protocol is our Achilles' heel. Those who breach isolation are everybody's problem. This is how the disease is spreading now and how variants get into the country. The isolation rule must be on all our minds," he said.
"If a child was abroad and goes to school tomorrow, that is wrong, and everybody should tell them and their parents that."
Currently around 65% of Israel's population have been vaccinated or have recovered from COVID-19, the Health Ministry says.