All viruses, including SARS-CoV-2, the virus that causes COVID-19, changes over time. The World Health Organisation (WHO) has divided the variants into two categories:
- Variants of Concern (VOC) – These are variants with clear clinical correlation evidence of an increase in transmissibility, severe disease severity, reduced effectiveness of treatments or vaccines, or diagnostic detection failures
| WHO label | Earliest documented samples | Date of Designation |
| Alpha | The United Kingdom, Sep-2020 | December 18, 2020 |
| Beta | South Africa, May-2020 | December 18, 2020 |
| Gamma | Brazil, Nov-2020 | January 11, 2021 |
| Delta | India, Oct-2020 | VOI: April 4, 2021
VOC: May 11, 2021 |
- Variants of Interest (VOI) – This is a variant with reduced neutralisation by antibodies generated against previous infection or vaccination, reduced efficacy of treatments, potential diagnostic impact, or predicted increase in transmissibility or disease severity.
| WHO label | Earliest documented samples | Date of Designation |
| Lambda | Peru, Dec-2020 | June 14, 2021 |
| Mu | Colombia, Jan-2021 | August 30, 2021 |
| Kappa | India, Oct-2020 | April 4, 2021 |
| Zeta | Brazil, April-2020 | March 17, 2021 |
| Theta | Philippines, Jan-2021 | March 24, 2021 |
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