The Omicron coronavirus variant is better at circumventing vaccinated peoples' immunity than the Delta variant, according to a Danish study published last week, helping explain why Omicron is spreading more rapidly.

Since the discovery of the heavily mutated Omicron variant in November, scientists have been racing to find out whether it causes less serious disease and why it appears more contagious than the previously dominating Delta variant.

A virus can be more transmissible due to a number of reasons, such as the time it lingers in the air, its ability to latch...