Data from Israel on Thursday supported growing evidence worldwide that Omicron causes milder illness than previous variants of the coronavirus even as the country grappled with a record number of daily infections.

Total hospitalisations on Wednesday stood at 363 patients, after the Health Ministry reported more than 16,000 new cases – a record high in Israel since the start of the pandemic – with a daily increase of 32 more people falling severely ill.

During the height of Israel’s Delta variant wave, the record number of people infected topped 11,000, with the number of those falling severely ill increasing daily by around 100 and 1,300 people hospitalized.

“Our initial data, which is not yet entirely accurate, points to seven to eight people hospitalised for 1,000 infected, two of whom will fall severely ill or worse,” Sharon Alroy-Preis, the ministry’s head of public health, told Army Radio.

“This is a significant change from Delta which saw far more – at least 10 severely ill for every 1,000 infections,” she said.

Israel has confirmed around 1.4 million infections since the start of the pandemic and more than 8,000 deaths.

The World Health Organization said on Tuesday that more evidence was emerging of Omicron causing milder symptoms than previous variants and resulting in a “decoupling” in some places between soaring case numbers and low death rates.

Nonetheless, health officials are concerned that even if Omicron is less harmful, its fast surge could overload healthcare systems.

Jerusalem’s Hadassah Medical Center opened its second coronavirus ward on Thursday as coronavirus admissions rose.

“We get the impression that Omicron causes a disease that is not as severe as the previous variants. However, there is still a high level of uncertainty because we need perspective, we need to see after a period of time how many severe cases we accumulate,” said Hadassah’s head of medicine Alon Hershko.

With infections rising fast, Israel’s testing centres have been buckling under the pressure, prompting health officials to prioritise risk groups and trust younger, vaccinated populations to test at home if exposed to a carrier.

Risk groups have also been green-lighted for a fourth dose of a COVID-19 vaccine and for Pfizer Inc and Merck & Co Inc’s antiviral COVID-19 medications.

A week into a fourth dose trial at a major Israeli hospital, researchers saw participants’ antibody levels increase five-fold.

But Gili Regev-Yochay, who is leading Sheba Medical Centre’s study, said that while the jump restored protection provided by a third dose, it was lower than what she had hoped for.

“I expect to see it continue rising, the peak of antibodies usually occurs two to four weeks in,” she told Army Radio.

Hershko said that so far, as in the Delta wave, unvaccinated patients largely suffered more severe COVID-19 than vaccinated ones and made up the majority of admissions. Around 60% of the country’s 9.4 million population is vaccinated.