Reuters Reuters 21 July, 2021, 2:10 pm Vials labelled "Moderna, Johnson & Johnson, Pfizer-BioNTech coronavirus disease (COVID-19) vaccine" are seen in this illustration picture taken May 2, 2021. REUTERS/Dado Ruvic CHICAGO, July 20 (Reuters) – Scientists are working on a benchmark for COVID-19 vaccine efficacy that would allow drugmakers to conduct smaller, speedier human trials to get them to market and address a huge global vaccine shortage. Researchers are trying to determine just what level of COVID-19 antibodies a vaccine must produce to provide protection against the illness. Regulators already use such benchmarks – known as correlates of protection – to evaluate flu vaccines without requiring large, lengthy clinical trials.