Updated 5 hours ago NBC Universal, Inc. Los Angeles County health officials are once again asking their residents -- even the fully vaccinated ones -- to mask up, this time against a newer and more transmissible variant of the COVID-19 disease. The World Health Organization is also urging fully vaccinated people to wear masks so the variant doesn’t spread to unvaccinated people. Download our NBC 7 mobile app for iOS or Android to get alerts for local breaking news and weather. The World Health Organization says the Delta variant is so contagious that even vaccinated people ought to wear masks, so the variant doesn't spread to unvaccinated people. NBC News medical correspondent Dr. John Torres talks about the variant and whether the U.S. would need to reinstitute mask mandates in the face of it.