This variant, or B.1.351, was identified in South Africa at the end of 2020 and spread to other countries. Experts had been concerned about its several mutations and its potential to evade antibodies. Beta was not common in the U.S.

How contagious is it? The CDC said Beta was about 50% more contagious than the original coronavirus strain.

Severity: There was evidence to suggest that Beta may have been more likely than other variants to lead to hospitalization and death.

Can vaccination prevent it? South Africa stopped offering the AstraZeneca-Oxford vaccine (which is not available in the U.S.) early in 2021 after clinical trials showed it did not provide strong protection against mild and moderate disease from the Beta variant. Pfizer-BioNTech, Moderna, and Johnson & Johnson also reported less protection against Beta.