Beginning October 7, Universal Studios Hollywood will require all guests aged 12 and up to show proof of full FDA or WHO-approved COVID-19 vaccination (a full 14 days after final dose was administered), or a negative test taken within 72 hours of visit, prior to entry to the theme park.
Regardless of vaccination status, face coverings are required to be worn at all times, both indoors and outdoors, when visiting the theme park. At Universal CityWalk, face coverings are required to be worn indoors.
Interestingly Universal Studios Hollywood has added that verification will take place when required based on theme park attendance, which could mean that enforcement may be low (or nonexistent) on slow park days.
To read Universal Studios Hollywood's full health and safety statement you can check out their official website here.