Variants of Concern (VOCs) and Testing

As a virus replicates in its host’s cells, small changes can occur in its genes. Sometimes these small changes, or mutations, can have significant impacts on how the virus behaves. A virus is known as a variant when it acquires enough genetic mutations to make it substantively different from the original genetic reference sequence but not enough to make it a different virus altogether. For SARS-CoV-2, the original reference sequences are generally the first ones collected in Wuhan, China, and in Washington, United States.

“Variant of Concern” (VOC) is a label given to SARS-CoV-2 variants that show evidence of an ability to cause more severe disease, be more easily transmitted, or evade treatments, diagnostics, or previous immunity from vaccination or natural infection. To date, VOCs have included the Alpha, Delta, and Omicron variants, among others.

Genetic changes in variants can influence the accuracy of some COVID-19 tests when the variant’s genetic sequence is different enough from existing tests that these tests cannot detect the variant. Some COVID-19 tests look for multiple SARS-CoV-2 genes while other tests only detect a single gene. Too many changes in these target genes can reduce the ability of a test to detect the virus. Since multi-target tests look for more than one marker of infection, they tend to be less affected by genetic changes in variants. However, it is possible for a variant with enough mutations in key genes to avoid detection by even multi-target tests. This page contains information about SARS-CoV-2 Variants of Concern (VOC) and which COVID-19 tests have recorded a decreased ability to detect them. More information can be found on the FDA website.