SARS-CoV-2 variants: National definitions, classifications and public health actions

Last updated: December 23, 2021

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The Public Health Agency of Canada, in collaboration with provincial and territorial public health authorities, established the Canadian SARS-CoV-2 Variant Surveillance Group (CSVSG) to monitor and assess the impact of variants of SARS-CoV-2 on viral transmissibility, disease severity, and efficacy of vaccines, therapeutics, and diagnostics. The CSVSG has developed national definitions, classifications, and public health actions for SARS-CoV-2 Variants of Interest (VOI) and Variants of Concern (VOC), and sub-lineages descended from those VOC and VOI.

Variant of concern

Definition

A SARS-CoV-2 variant is a variant of concern if, through a comparative assessment, it has been demonstrated to be associated with one or more of the following:

or

is otherwise assessed to be a VOC by WHO;

or

is otherwise assessed to be a VOC by the CSVSG.

Actions

If a variant is determined to be a VOC, actions may include the following:

Table 1. Variants of concern. Updated December 23, 2021
WHO label Pango lineagesTable 1 footnote * Attributes Designation date
Alpha B.1.1.7 and Q lineages Evidence of increased transmissibility Footnote 1
Evidence of increased severity Footnote 2Footnote 3
Evidence of reduced neutralization by convalescent sera and post-vaccination sera Footnote 4Footnote 5Footnote 6
May 14, 2021
Beta B.1.351 and AZ lineages Evidence of increased transmissibility Footnote 1
Evidence of increased severity Footnote 7
Evidence of impact on neutralization by polyclonal antibodies Footnote 8
Evidence of reduced neutralization by convalescent sera and post-vaccination sera Footnote 4Footnote 9Footnote 10
May 14, 2021
Gamma P.1 Evidence of increased transmissibility Footnote 1
Evidence of increased severity Footnote 11Footnote 12
Evidence of impact on neutralization by polyclonal antibodies Footnote 8
Evidence of reduced neutralization by convalescent sera and post-vaccination sera Footnote 13
May 14, 2021
Delta B.1.617.2 and AY lineages Evidence of increased transmissibility Footnote 1
Evidence of increased severity Footnote 14Footnote 15
Evidence of impact on neutralization by polyclonal antibodies Footnote 16Footnote 17
Evidence of reduced neutralization by convalescent sera and post-vaccination sera Footnote 4Footnote 5
July 20, 2021
Omicron B.1.1.529 and BA lineages

Evidence of increased transmissibilityFootnote 18
Preliminary evidence of increased risk of reinfectionFootnote 19
Preliminary evidence of reduced neutralization by post-vaccination seraFootnote 20,Footnote 21

November 28, 2021
*Includes all descendant lineages

Variant of interest

Definition

A SARS-CoV-2 variant is a VOI if it

has a genome with mutations associated with changes in epidemiology, antigenicity, or virulence, or changes that potentially have a negative impact on available diagnostics, vaccines, therapeutics, or public health measures;

and

is known to cause community transmission/multiple COVID-19 cases/clusters in Canada or has been detected in multiple countries;

or

is otherwise assessed to be a VOI by WHO;

or

is otherwise assessed to be a VOI by the CSVSG.

Actions

If a variant is determined to be a VOI, actions may include the following:

Table 2. Variants of interest. Updated December 23, 2021
WHO label Pango lineages* Attributes Designation date
Eta B.1.525

Evidence of increased transmissibility Footnote 1

Predicted reduction in neutralization by some monoclonal antibody therapies

Predicted reduction in neutralization by polyclonal antibodies in convalescent sera

May 14, 2021
Mu B.1.621

Predicted reduction in neutralization by some monoclonal antibody therapies

Predicted reduction in neutralization by polyclonal antibodies

Predicted reduction in neutralization by convalescent sera and post-vaccination sera

August 05, 2021
n/a B.1.1.318

Predicted reduction in neutralization by some monoclonal antibody therapies

Predicted reduction in neutralization by polyclonal antibodies in convalescent sera

May 14, 2021
*Includes all descendant lineages

De-escalation

The SARS-CoV-2 virus continuously evolves, generating new lineages. Over time, some lineages may become prevalent while others will become extinct and no longer pose a threat to public health. VOCs and VOIs are de-escalated if they have not been observed to circulate in Canada for sixteen continuous weeks or where the evidence demonstrates that, relative to currently circulating lineages, they are no longer responsible for an increase in transmission or severe disease, and do not demonstrate decreased effectiveness of available diagnostics, vaccines, therapeutics, or public health measures. Canada's de-escalation strategy may change as circumstances prescribe. VOCs and VOIs that are de-escalated will continue to be monitored and assessed for changes or resurgences.

Table 3. De-escalated variants. Last updated December 23, 2021
WHO label Pango lineages* Attributes De-escalation Date
Epsilon B.1.427
B.1.429
Evidence of increased transmissibility Footnote 1
Evidence of moderate neutralization by some monoclonal antibody therapies Footnote 8
November 12, 2021
Zeta P.2

Predicted reduction in neutralization by some monoclonal antibody therapies

Predicted reduction in neutralization by polyclonal antibodies in convalescent sera

September 09, 2021
Theta P.3

Predicted reduction in neutralization by some monoclonal antibody therapies

Predicted reduction in neutralization by polyclonal antibodies in convalescent sera

December 09, 2021
Iota B.1.526

Evidence of increased transmissibility Footnote 1

Predicted reduction in neutralization by some monoclonal antibody therapies

Predicted reduction in neutralization by polyclonal antibodies in convalescent sera

December 09, 2021
Kappa B.1.617.1 Evidence of increased transmissibility Footnote 1
Preliminary evidence of impact on neutralization by convalescent and post-vaccination sera Footnote 16Footnote 17
October 01, 2021
Lambda C.37 Preliminary evidence of moderate reduction in neutralization by convalescent and post-vaccine seraFootnote 22 December 09, 2021
n/a A.23.1 Predicted reduction in neutralization by some monoclonal antibody therapies
Predicted reduction in neutralization by polyclonal antibodies in convalescent sera
October 14, 2021
n/a B.1.617.3 Predicted reduction in neutralization by polyclonal antibodies
Predicted reduction in neutralization by convalescent sera and post-vaccination sera
July 20, 2021
*Includes all descendant lineages.

References

Footnote 1

Campbell, F et al. (2021) Increased transmissibility and global spread of SARS-CoV-2 variants of concern as at June 2021. Eurosurveillance doi: https://doi.org/10.2807/1560-7917.ES.2021.26.24.2100509

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Footnote 2

Davies, N. G. et al. (2021) Increased mortality in community-tested cases of SARS-CoV-2 lineage B.1.1.7. Nature doi: https://doi.org/10.1038/s41586-021-03426-1

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Footnote 3

Challen, R. et al. (2021) Risk of mortality in patients infected with SARS-CoV-2 variant of concern 202012/1: matched cohort study. BMJ doi: http://doi.org/10.1136/bmj.n579

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Footnote 4

Nasreen, S. et al. (2021) Effectiveness of COVID-19 vaccines against variants of concern, Canada. medRxiv, doi: https://doi.org/10.1101/2021.06.28.21259420

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Footnote 5

Bernal, J. L. et al. (2021) Effectiveness of COVID-19 vaccines against the B.1.617.2 variant. medRxiv, doi: https://doi.org/2021.05.22.21257658

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Footnote 6

Cele, S. et al. (2021) Escape of SARS-CoV-2 501Y.V2 from neutralization by convalescent plasma. Nature, doi: https://doi.org/10.1038/s41586-021-03471-w

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Footnote 7

Jassat, W. et al. (2021) Increased mortality among individuals hospitalised with COVID-19 during the second wave in South Africa. bioRxiv, doi: https://doi.org/10.1101/2021.03.09.21253184

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Footnote 8

US FDA (2021) U. S. Fact sheet for health care providers emergency use authorization (Eua) of bamlanivimab and etesevimab. https://www.fda.gov/media/145802/download

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Footnote 9

Madhi, S. A. et al. (2021)Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant. N. Engl. J. Med. doi: https://doi.org/10.1056/NEJMoa2102214

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Footnote 10

Lustig, Y. et al. (2021) Neutralizing Response against Variants after SARS-CoV-2 Infection and One Dose of BNT162b2. N. Engl. J. Med., doi: https://doi.org/10.1056/NEJMc2104036

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Footnote 11

Funk, T. et al. (2021) Characteristics of SARS-CoV-2 variants of concern B.1.1.7, B.1.351 or P.1: data from seven EU/EEA countries, weeks 38/2020 to 10/2021. Eurosurveillance, doi:https://doi.org/10.2807/1560-7917.ES.2021.26.16.2100348

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Footnote 12

Freitas, A. R. R. et al. (2021) The increase in the risk of severity and fatality rate of covid-19 in southern Brazil after the emergence of the Variant of Concern (VOC) SARS-CoV-2 P.1 was greater among young adults without pre-existing risk conditions. bioRxiv, doi: https://doi.org/10.1101/2021.04.13.21255281

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Footnote 13

Wang, P. et al. (2021) Increased Resistance of SARS-CoV-2 Variant P.1 to Antibody Neutralization. CSHL, doi: https://doi.org/10.1101/2021.03.01.433466

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Footnote 14

Sheikh, A. et al. (2021) SARS-CoV-2 Delta VOC in Scotland: demographics, risk of hospital admission, and vaccine effectiveness. Lancet, doi: https://doi.org/10.1016/S0140-6736(21)01358-1

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Footnote 15

Ong, S. W. X. et al. (2021). Clinical and Virological Features of SARS-CoV-2 Variants of Concern: A Retrospective Cohort Study Comparing B.1.1.7 (Alpha), B.1.315 (Beta), and B.1.617.2 (Delta). SSRN, doi: https://doi.org/10.2139/ssrn.3861566

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Footnote 16

Hoffmann, M. et al. (2021) SARS-CoV-2 variant B.1.617 is resistant to Bamlanivimab and evades antibodies induced by infection and vaccination. bioRxiv, doi: https://doi.org/10.1101/2021.05.04.442663

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Footnote 17

Liu, C. et al. (2021) Reduced neutralization of SARS-CoV-2 B.1.617 by vaccine and convalescent serum. Cell, doi: https://doi.org/10.1016/j.cell.2021.06.020

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Footnote 18

European Centre For Disease Control (2021) Threat Assessment Brief: Implications of the further emergence and spread of the SARS CoV 2 B.1.1.529 variant of concern (Omicron) for the EU/EEA first update. https://www.ecdc.europa.eu/en/publications-data/covid-19-threat-assessment-spread-omicron-first-update

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Footnote 19

Pulliam, J.R.C. et al. (2021) Increased risk of SARS-CoV-2 reinfection associated with emergence of the Omicron variant in South Africa. bioRxiv, doi : https://doi.org/10.1101/2021.11.11.21266068

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Footnote 20

Pfizer and BioNTech (2021) Update on Omicron Variant. Press Release, https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-provide-update-omicron-variant

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Footnote 21

Cele, S. et al. (2021) SARS-CoV-2 Omicron has extensive but incomplete escape of Pfizer BNT162b2 elicited neutralization and requires ACE2 for infection. In bioRxiv. https://doi.org/10.1101/2021.12.08.21267417

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Footnote 22

Tada, T. et al. (2021) SARS-CoV-2 Lambda Variant Remains Susceptible to Neutralization by mRNA Vaccine-elicited Antibodies and Convalescent Serum. bioRxiv, doi: https://doi.org/10.1101/2021.07.02.450959

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