LOS ANGELES—Responding to concerns from the theme park industry, Los Angeles County has slightly eased its upcoming COVID-19 vaccination or testing requirement for visitors to large venues such as Six Flags Magic Mountain and Universal Studios Hollywood, but the overall mandate will remain. Under a recently enacted county Health Officer Order, all attendees and employees at outdoor mega-events with 10,000 people or more will have to show proof of COVID-19 vaccination or a negative test within 72 hours, with the mandate taking effect Oct. 7. The order will apply to large theme parks, which were recently re-categorized by the state as a large outdoor event venue. Theme parks in the county, along with an industry association, expressed concerns about the requirement, contending they had limited staffing to check the required documentation—both a vaccine or testing verification and a photo ID—potentially leading to long lines for admission to the parks. They …