On May 26, 2021, Altimmune announced new results from a preclinical study demonstrating the ability of its AdCOVID vaccine candidate to neutralize the rapidly emerging SARS-CoV-2 B.1.351 variant of concern that originated in South Africa. B.1.351 carries multiple mutations in the receptor binding domain including the E484K mutation that has been shown to substantially decrease the ability of authorized vaccines to neutralize the virus.