More research on the delta variant of SARS-CoV-2 reports that this viral mutant is the most dangerous one to date. It spreads more easily and may cause more serious infections. It accounts for more than half of infections in the United States and is spreading rapidly in counties with low vaccination rates. The good news is that fully vaccinated people show strong protection against the delta variant. Protection after only one dose is not near as robust. People who have been infected with a previous version of SARS-CoV-2 are not protected against reinfection by the delta variant. Yet another reason to get the vaccine. A news article about the paper is available at ASM and the original paper is in Nature.