Omicron is spreading at lightning speed. Scientists are trying to figure out why

In late November, more than 110 people gathered at a crowded Christmas party at a restaurant in Oslo, Norway. Most of the guests were fully vaccinated. One had returned from South Africa just a few days earlier and was unknowingly carrying the omicron variant of SARS-CoV-2.

Ultimately, about 70% of the partygoers were infected.

Scientists who traced this superspreader event concluded it was evidence that omicron was “highly transmissible” among fully vaccinated adults.