By Alisa Odenheimer

Israel is making preparations to ensure it has sufficient vaccine supply in case a fourth round of Covid-19 shots is needed, the country’s top health official said on Sunday.

“We don’t know when it will happen; I hope very much that it won’t be within six months, like this time, and that the third dose will last for longer,” Health Ministry Director General Nachman Ash said in an interview with Radio 103FM.

Israel, which has mainly used the Pfizer Inc.-BioNTech SE vaccine, has so far inoculated about 2.8 million people with a third dose after beginning a drive to administer booster shots in August. Health officials have said the effects of the initial Covid-19 shots weaken five months after inoculation, making boosters necessary.

The U.S. and U.K. also plan to start offering booster shots later this month, while Europe is also considering third doses. That comes as the World Health Organization pleads for a moratorium on third shots. Director-General Tedros Adhanom Ghebreyesus said last week that governments should wait at least until the end of this year so that poorer countries can get better access to vaccines.

In addition to those who have received boosters, about another 2.7 million of the 7 million eligible Israelis have had two jabs and about 500,000 have had just one shot. Almost 1 million people haven’t had any vaccine doses.

The country, once a front-runner in the global race to move on from Covid-19, became a pandemic hot spot in early September. Following the spread of the delta variant over the summer, Israel had the world’s highest per-capita infection rate in the week through Sept. 4, according to figures compiled by Johns Hopkins University.

Ash said last week that the booster shots appear to have halted the surge in infections.

The rate of severe cases per 100,000 of the population among unvaccinated people is far higher than among those who have received two vaccine doses, showing that even with waning immunity, shots provide some protection against serious illness.

Asked about a report that Israel had promised Pfizer that it would use the company’s vaccine exclusively, Ash said that the government had made no such undertaking. He said that people over the age of 18 getting their first shots are currently being given the Moderna Inc. vaccine.