High SARS-CoV-2 vaccine effectiveness in California, even with variants Researchers in the United States and the UK have conducted a study showing that the rollout of vaccines to protect against coronavirus disease 2019 (COVID-19) is proving effective among California's general population. The population-based surveillance study found that vaccination efforts are preventing infection with the causative agent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) under real-world conditions, despite the widespread circulation of variants of concern. Working on behalf of the California COVID-19 Case-Control Study Team, the researchers found that among fully vaccinated individuals (the second dose received two weeks or more previously), protection against SARS-CoV-2 infection was 86%.