A side-by-side comparison of the Pfizer/BioNTech and Moderna vaccines

In an ideal world, a pandemic vaccine could be delivered in a single shot, so supplies could be stretched to cover a lot of people. It would trigger no side effect more significant than a sore arm. And it would be easy to ship and store.

Unfortunately, this is not an ideal world — not yet, anyway.

For now, the good news is that the United States has two Covid-19 vaccines that have been shown to be highly effective.