As Worries Mount About Omicron, What to Know About Other Variants of Concern

Omicron, the newest COVID variant of concern, has the potential to be more transmissible and evade vaccines but it's not the only worrisome variant being tracked by the World Health Organization (WHO).

The WHO classified Omicron as a variant of concern on Friday, warning that its more than 30 mutations are associated with increased transmissibility and potential resistance to vaccines and treatments. It's the fifth variant to be classified as a variant of concern since the start of the pandemic and experts believe it's already spread to most, if not every, country on the planet.

Omicron was first detected in South Africa on November 24, but the sequence was collected on November 9, indicating the variant had been spreading for at least a few weeks. Primary evidence indicates it has a higher risk of reinfections than other variants of concern. However, it could be a few weeks before data shows if it's more infectious or dangerous than Delta, the dominant variant of concern.


The B.1.617.2 variant, dubbed Delta, was first identified in India in October 2020. The WHO designated it a variant of interest in April 2021 and then upgraded it to a variant of concern in May. It's since become the dominant variant worldwide and has shown to be so transmissible that it's prevented several variants of interest from taking hold.

To be a variant of concern, a variant must be either more transmissible, cause more serious disease than other strains or render vaccines, testing or therapeutics less effective.

Along with being more transmissible than other variants, Delta increases a person's risk of being hospitalized with COVID-19 and their chances at being reinfected. That's largely fueled by its decrease in antibody protection, both from the vaccine and recovering from a COVID-19 infection.

omicron variants of concern
The World Health Organization (WHO) is tracking five variants of concern, including Alpha, Beta, Gamma, Delta and Omicron. Pictured, World Health Organization (WHO) Director-General Tedros Adhanom Ghebreyesus attends a ceremony to launch of a multiyear partnership with Qatar ahead of FIFA Football World Cup 2022 at the WHO headquarters in Geneva on October 18. Fabrice Coffrini/Pool/AFP/Getty Images


Months before Delta raised a red flag, the WHO designated Gamma, P.1, as a variant of concern in January. It was first detected in Brazil in November 2020 and also showed a possible increased risk of a person becoming seriously ill and being hospitalized with COVID-19.

It's since been overtaken by Delta and accounts for only about 0.1 percent of COVID-19 cases around the world, according to the WHO.


B.1.351, also known as Beta, was first detected in South Africa in May 2020, just months after the pandemic began. It's even less prevalent than the Gamma variant, accounting for fewer than 0.1 percent of all COVID-19 cases globally, according to the WHO.

Similarly to the other variants of concern, Beta has shown to be more transmissible and increases a person's risk of being hospitalized. The variant also increased a person's chances of dying of COVID-19 after being hospitalized.


Alpha, designated B.1.1.7, was the first variant of concern to be identified by the World Health Organization. It received its designation on the same day as the Beta variant, but was first identified months after Beta, in the United Kingdom in September 2020.

Also accounting for fewer than 0.1 percent of global COVID-19 cases, the variant has increased transmissibility and showed to cause more severe disease and death than the original strain. However, it didn't seem to increase a person's risk of reinfection.

Along with the five variants of concern, the WHO is tracking two variants of interest. Both Mu and Lambda have shown to be more dangerous than the original variant and have shown to cause significant community transmission in multiple countries.