How does Johnson & Johnson's COVID-19 vaccine stack up against shots from Pfizer and Moderna?

Vials of the Pfizer-BioNTech Covid-19 vaccine.
Patrick Fallon/AFP via Getty Images
Johnson & Johnson's COVID-19 vaccine was shown to be 66% effective at preventing mild and moderate infections, and 85% effective at preventing severe disease, in FDA data released Wednesday.
It doesn't appear to be as effective as Moderna or Pfizer's mRNA vaccines, though it is nearly just as good at preventing hospitalizations and deaths.
It has the benefits of being cheap and relatively easy to manufacture