Johnson & Johnson on Monday started Phase 3 trials of its coronavirus vaccine, something three of its big US competitors have already done. But the New York Times points out that Johnson & Johnson's candidate is an appealing one, in that it may end up being a single-dose vaccine. And unlike Moderna and Pfizer's vaccines, which use mRNA and require sub-zero temperature storage, Johnson & Johnson's only needs standard refrigeration. Those two companies already have clinical trials underway; AstraZeneca's Phase 3 trial has been paused. Johnson & Johnson's planned 60,000 participants across three continents make it the largest of those four trials, which could "provide a faster readout," per virologist Dr. Daniel Barouch.
The trial will compare the vaccine with a placebo by tracking the symptomatic Covid-19 rates among the two groups. NBC News reports Johnson & Johnson could have preliminary results in two months. The company hopes it might be able to determine whether it works by early 2021, with the Wall Street Journal reporting that if all goes well, the feds could OK it for emergency use soon after. How the vaccine works: The vaccine puts an adenovirus to work. It carries a gene from the coronavirus in cells that then create coronavirus proteins—but not the coronavirus. The adenovirus vaccine was developed about 20 years ago, and since acquiring it, Johnson & Johnson has used it to make four vaccines that have been administered about 100,000 times in total: for Ebola, HIV, RSV, and Zika. (Read more coronavirus stories.)