How do the three Covid-19 vaccines compare?They all work well, health experts say. The Pfizer-BioNTech and Moderna shots were more than 94% effective at preventing Covid-19 in their late-stage trials, while J&J’s effectiveness was 66%.
But the difference may be less than it seems. The Pfizer-BioNTech and Moderna shots were tested before the emergence of strains like one first identified in South Africa, which various studies have indicated eludes vaccines somewhat, though they still work against it.
J&J’s vaccine was tested in South Africa, and its effectiveness wasn’t as high there as in other countries, hurting the vaccine’s overall effectiveness.