Graduation parties in Mequon, Thiensville are linked to an uptick in coronavirus cases in young adults, health officials say

From JSOnline:

Jeff Rumage

Milwaukee Journal Sentinel

Graduation parties in Mequon and Thiensville have been linked to a recent uptick in coronavirus cases in young adults, according to local public health officials.

When a person tests positive with the coronavirus, public health officials interview them about their symptoms, where they had been and with whom they had interacted.

That process, called contact tracing, led the Washington Ozaukee Public Health Department to conclude that a recent cluster of new cases among young adults was due to large gatherings, including several graduation parties in Mequon and Thiensville.

Read more: https://www.jsonline.com/story/communities/northshore/news/mequon/2020/08/06/coronavirus-uptick-linked-graduation-parties-mequon-thiensville/3309383001/

I'm sick of reading stories like this.  Why do some groups of people think that they are invulnerable to COVID-19?