The most widely used coronavirus vaccines are designed as two-shot inoculations, and nearly everyone worldwide who has had both doses has received the same vaccine both times.

But that is changing, as more countries are allowing — and even, in some cases, encouraging — mix-and-match inoculation, with people receiving a first shot of one vaccine, and then a second shot of a different one. On Tuesday, Germany’s government revealed that Chancellor Angela Merkel had received two different shots, adding to the growing interest in the practice.

JERUSALEM — Israel has been a trailblazer in the post-pandemic world, largely returning to normal in May following one of the world’s fastest vaccination drives.

But dozens of new cases recently emerged at schools in two cities, Modiin and Binyamina, leading to hundreds of people being quarantined. Israel has made 12- to 15-year-olds eligible for vaccination, but many have yet to get shots.