mRNA COVID vaccination tied to 80% lower risk of asymptomatic infectionA real-world Mayo Clinic study shows a link between vaccination with two doses of an mRNA-based COVID-19 vaccine—either Pfizer/BioNTech or Moderna—and an 80% lower risk of asymptomatic infection.The retrospective cohort study, published yesterday in Clinical Infectious Diseases, involved 39,156 asymptomatic adult COVID-19 patients screened for SARS-CoV-2 infection using 48,333 preprocedural tests from Dec 17, 2020, to Feb 8, 2021.Forty-two (1.4%) of 3,006 tests of patients who had received at least one dose of vaccine were positive for COVID-19, compared with 1,463 (3.2%) of 45,327 tests of unvaccinated patients (relative risk [RR], 0.44).Compared with unvaccinated