Alpha (B.1.1.7) was the first of the highly publicized variants. Alpha first appeared in Great Britain in November 2020 and infections surged in December of that year. It soon surfaced around the world and became the dominant variant in the U.S., where the CDC classified it as a variant of concern. Then, Alpha faded away with the rise of the more aggressive Delta variant.

How contagious is it? Some mutations in Alpha’s spike protein were thought to make it more infectious. The B.1.1.7 lineage was believed to be 30 to 50% more contagious than the original SARS-CoV-2 strain. In the U.S., in mid-April 2021—before Delta became predominant—Alpha comprised 66% of cases, according to a study released in June by the CDC.

Severity: Studies have suggested the B.1.1.7 lineage was more likely to land infected people in the hospital and was deadlier than the original virus.

Can vaccinations prevent it? Pfizer, Moderna, and Johnson & Johnson all said their vaccines were effective in preventing severe disease and hospitalization in Alpha cases.

This article was medically reviewed by Yale School of Public Health epidemiologist Nathan Grubaugh, PhD.

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