In his inaugural speech to the Israeli parliament, Prime Minister Naftali Bennett addressed an impressively detailed list of the challenges his ruling coalition faces. Only one issue went unmentioned: the fight against Covid-19. As far as the prime minister and public were concerned, the pandemic was over, the virus vanquished by Israel’s world-leading vaccination campaign.

That belief lasted a week. In mid-June, new and alarming cases of the virus began to sprout. The Delta variant was responsible, experts said. It was being imported by Israelis returning from abroad. A large percentage of those infected were children...