The CDC and FDA recommend that everyone 18 and older who received the Johnson & Johnson COVID-19 vaccine get an additional dose, at least two months out. Across the globe, the J&J vaccine has been quite popular precisely because it’s a single-dose vaccine that’s easier to administer in hard-to-reach places. The World’s Elana Gordon tells host Carol Hills how researchers in South Africa are unpacking the benefits of a single shot and a possible second one.