The Johnson & Johnson (J&J) adenovirus-based COVID-19 vaccine is 74% effective in preventing SARS-CoV-2 infection even amid phases of high Alpha (B117) and Delta (B1617.2) variant circulation, according to the preliminary findings of a real-world US study yesterday in JAMA Network Open.The comparative-effectiveness study, led by researchers from nference, a Massachusetts software company affiliated with Janssen, maker of the J&J vaccine, involved mining the Mayo Clinic electronic health records (EHRs) of 8,889 vaccinated and 88,898 matched unvaccinated adults living in 1 of 15 states from Feb 27 to Jul 22, 2021.The EHRs were from the multistate Mayo Clinic Health System.