By CBSLA Staff

LOS ANGELES (CBSLA) — All attendees at indoor events in California with over 1,000 people must show proof of COVID-19 vaccination or a negative COVID test within 72 hours of the event, the state Department of Public Health announced Wednesday.

The new rules will take effect on Sept. 20.

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Prior to Wednesday’s announcement, the state was allowing people to “self-attest” to being vaccinated or having tested negative. The previous guidelines also applied only to events with 5,000 or more people, but the new rules lower the threshold to 1,000.

“The Delta variant has proven to be highly transmissible, making it easier to spread in large crowds where people are near each other for long periods of time,” said Dr. Tomas Aragon, the state public health officer. “By requiring individuals to be vaccinated, or test negative for COVID-19 at large events, we are decreasing the risk of infection, hospitalization and death.”

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The announcement is the latest in a series of vaccination or testing mandates imposed in a variety of sectors.

Meanwhile Wednesday, the Los Angeles City Council voted to impose such a mandate on its workers, and the city of Santa Ana announced a similar requirement.

Starting Thursday at 11:59 p.m., Los Angeles County will impose a mask-wearing mandate for all attendees at outdoor “mega-events” with 10,000 or more people.

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(© Copyright 2020 CBS Broadcasting Inc. All Rights Reserved. City News Service contributed to this report.)