7 looming questions about the rollout of a Covid-19 vaccine

The race to develop Covid-19 vaccines could well see some Americans vaccinated before the end of 2020 — less than a year after the world first learned a new virus was causing a dangerous new form of pneumonia in China.

The design, testing, and mass production of multiple vaccines has never been attempted on this type of timeline, making this moment a turning point in the development of vaccines to respond to new disease threats.