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Like most viruses, the COVID virus (SARS-CoV-2) spreads by using human cells as hosts to make copies of itself. Sometimes, these copies have “typos” in their genetic code. And sometimes, these copies make the virus better able to reproduce or spread among its human hosts. These mutations become “variants of concern” when they are more contagious, cause more severe symptoms, or are less responsive to treatments or vaccines.  Here is a current list of the SARS-CoV-2 variants of concern, as well as some “variants of interest” – those which have the potential to become a variant of concern.


This variant, also known as B.1.671.2, is the variant of greatest concern. It was first identified in India in December and quickly became the dominate strain around the world. Arriving in the U.S. in March, it now accounts for over 80% of all new cases here. Delta appears to be the most contagious variant discovered thus far; it also might be able to short-circuit some immune defenses via a mutation similar to Eek – though data are still be evaluated regarding both claims. Both Pfizer and Moderna are effective against serious illness or death from Delta-COVID infection, though both doses are required. It is still unclear how effective Johnson & Johnson is against this viral variant. There is some evidence that some asymptomatic vaccinated people could transmit the virus to others if they are exposed.

Delta FAQs


Formerly known as the B.1.1.7 variant, it first appeared in the United Kingdom last September. The alpha variant quickly spread, and by April was the dominant strain in the U.S. This variant is about 50% more contagious than the original virus and there is some evidence that it is also more deadly. The mutations in this virus seem to allow it to bind more tightly to cells, which could account for more severe symptoms, and to stay in the body longer, which could give it more time to be transmitted to others.


Also known as B.1.351, this variant also first appeared in September, but in South Africa. It quickly took over the country and made its way to the U.S. in January, but it has since diminished significantly since then and is responsible for only a few cases in the world today. There have been no cases detected in the U.S. in the past several weeks. This variant also appears to be about 50% more contagious than the original virus. It also includes the “Eek” mutation (E48K), which seems to allow the virus to get around human immune defenses more effectively. In particular, the AstraZeneca vaccine is not effective against this variant causing mild or moderate cases of COVID. The Johnson & Johnson vaccine is only 57%-72% effective against this variant. The Pfizer and Moderna vaccines retain more effectiveness.


Also known as P.1, the variant originated in Brazil in December. It quickly spread across South America. Importantly, the gamma variant can reinfect people who had been infected with the original COVID. It still comprises approximately 90% of the cases in Brazil. Gamma was first detected in the U.S. in January. Six months later, it comprised about 11% of the cases and now hovers around 3%. This mutation also has the Eek variant and it appears to be about 2 times as contagious as the original.  Fortunately, our vaccines offer strong protection against this variant.

Variant of Interest

It is important to note that while most cases in the U.S. are the delta variant, scientists have cataloged additional variants that could pose additional risks.

  • Eta (variant B.1.525), which also contains the Eek mutation;
  • Iota (variant B.1.526), one version of which contains Eek and a second latches onto cells more readily;
  • Kappa (variant B.1.617.1), which is closely related to the delta variant;
  • Lambda (variant C.37), which appears similar to the alpha variant;
  • Epsilon, a variant that is deemed no longer to be a threat;
  • Zeta, a variant that is deemed no longer to be a threat;
  • Theta, a variant that is deemed no longer to be a threat.

The more the virus spreads, the more it will mutate. Vaccination will help stop viral infections and therefore on-going the chain of mutations – one of which could get around all our defenses.