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Vaccine terms explained: Efficacy vs. effectiveness, herd immunity and others

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February 4, 2021 at 8:00 a.m. EST
A pharmacist prepares a syringe with the Pfizer-BioNTech vaccine at Virginia Hospital Center in Arlington. (John McDonnell/The Washington Post)

This story has been updated.

After months of waiting, three highly effective coronavirus vaccines have received emergency use authorization from the Food and Drug Administration, But amid the rollout, there have been many questions about the vaccines. Here are the key vaccine-related terms you need to know.