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Viruses, including SARS-CoV-2 coronavirus, mutate all the time. Most changes aren't of concern, however some can make the virus more adept at infecting cells or evading antibodies. These variants are able to outcompete other strains. During replication, a virus often undergoes genetic changes that may create what are called variants. New variants become predominant through a process of evolutionary selection that is not well understood. Once identified, several questions arise regarding the potential clinical consequences of a new variant: Is it more readily transmitted; is it more virulent or pathogenic; and can it evade immunity induced by vaccination or prior infection?
The World Health Organization uses “variants of concern” to signify strains that pose additional risks to global public health, “variants of interest” for those that warrant close monitoring because of their emerging risk, and "alerts for further monitoring" for a variant that possesses genetic characteristics that indicate it may pose a future risk. Assessments may change depending on the evolving pandemic. For example, three variants of interest -- epsilon, zeta and theta -- were reclassified in early July as alerts. Variants of concern and variants of interest are assigned letters from the Greek alphabet for identification. As of July 7, the WHO has identified four in each category. Click here for more information on variants WHO is tracking.
The Delta variant is one of several variants of concerns. This variant is considerably more contagious than other COVID-19 strains, however early studies out of the UK do show that all FDA approved vaccines offer substantial protections against the Delta variant. Studies are being conducted to determine if Delta is more severe than previous strains. At this time, the main concern resulting from Delta is the much higher transmissibility rate.
On Nov 26th, another variant called the Omicron (sometimes called Nu) variant was added to the variants of concern list, and has been detected in the United States. The Omicron variant was originally sequenced in South Africa, but has since been found in multiple different countries from samples collected before the South Africa sequence. The Omicron variant appears to be extremely contagious, perhaps more so than Delta, but this is still being studied. Currently, Pfizer is expected to have information on how their vaccine holds up against the new variant in the coming weeks, while Moderna and Johnson & Johnson have not made any statements yet.
For information on the spread of variants, including Delta, in Oregon, please click here.
For CDC information on variants, please click here.