Johnson & Johnson is seeking emergency use authorization of its COVID-19 vaccine after a large clinical trial showed it was 66% effective at preventing moderate to severe disease four weeks after vaccination. The vaccine’s efficacy appeared to rise over time, with no cases of severe disease reported in recipients seven weeks after their shots. The Johnson & Johnson vaccine only requires a single dose and doesn’t require ultra-cold storage, making it easier to distribute than vaccines produced by Moderna and Pfizer. It’s also less expensive to produce. Johnson & Johnson says it’s ready to ship 100 million doses to the U.S. through June.