https://www.siliconvalley.com/2021/04/07/vaccine-passports-the-new-trend-in-california/

On Friday afternoon, as they have done for generations every spring, baseball fans will head to San Francisco for the Giants home opener.

But to enter the ballpark this year, they will need to bring something in addition to their ticket: proof they have been vaccinated or the results of a negative COVID-19 test taken within the past 72 hours.