A booster dose of Johnson & Johnson’s COVID-19 vaccine gives elevated protection against the virus that causes COVID-19, the company said Tuesday. Johnson & Johnson said data from a Phase 3 clinical trial its researchers are helping run showed that a second shot of its vaccine provides 75 percent protection against symptomatic COVID-19 globally, and 94 percent effective against symptomatic COVID-19 in the United States. The booster, when given two months after the first shot, caused antibody levels in recipients to rise four to six times higher than the levels observed after the single shot, the company said. The trial also tested giving the booster six months after the initial jab. In those cases, antibodies climbed nine-fold one week after the booster and kept climbing, to 12-fold higher, a month after the booster. The findings come from a trial dubbed ENSEMBLE 2 that is run by researchers with Janssen, a …