(Reuters) - Johnson & Johnson said on Friday that its single-dose vaccine was 66% effective in preventing COVID-19 in a large global trial against multiple variants which will give health officials another weapon to tackle the coronavirus. In the trial of nearly 44,000 volunteers, the level of protection against moderate and severe COVID-19 varied from 72% in the United States, to 66% in Latin America and just 57% in South Africa, from where a worrying variant has spread. A high bar has been set by two authorized vaccines from Pfizer/BioNTech and Moderna, which were around 95% effective in preventing symptomatic illness in pivotal trials when given in two doses. Those trials, however, were conducted mainly in the United States and before new variants emerged. The top U.S. infectious disease specialist Anthony Fauci said the variations in effectiveness around the world underlined the need to vaccinate as many people as quickly as possible to prevent new variants from emerging. “It