SARS-CoV-2 variants: National definitions, classifications and public health actions
Last updated: March 9, 2022
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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:
- increased transmissibility or detrimental change in COVID-19 epidemiology;
- increased virulence or change in clinical disease presentation;
- decreased effectiveness of available diagnostics, vaccines, therapeutics, or public health measures;
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:
- Notification to WHO under the International Health Regulations.
- Perform enhanced genomic and case-based surveillance.
- Submit complete genome sequences and accompanying contextual data to public sequence repositories (e.g., GISAID, INSDC).
- Perform epidemiological investigations that include appropriate disaggregation by age, sex, gender, race/ethnicity, Indigeneity, socioeconomic status, and geography/place of residence as data is available to improve understanding of the potential impacts of the VOC on COVID-19 spread, severity, the effectiveness of vaccines and public health measures, or other relevant characteristics.
- Perform laboratory investigations to assess the impact of the VOC on diagnostic methods, immune responses, antibody neutralization, or other relevant characteristics.
| WHO label | Pango lineages* | Attributes | Designation date |
|---|---|---|---|
| Alpha | B.1.1.7 and Q lineages | Evidence of increased transmissibility Footnote 1 Evidence of increased severity Footnote 2, Footnote 3 Evidence of reduced neutralization by convalescent sera and post-vaccination sera Footnote 4, Footnote 5, Footnote 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 4, Footnote 9, Footnote 10 |
May 14, 2021 |
| Gamma | P.1 | Evidence of increased transmissibility Footnote 1 Evidence of increased severity Footnote 11, Footnote 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 14, Footnote 15 Evidence of impact on neutralization by polyclonal antibodies Footnote 16, Footnote 17 Evidence of reduced neutralization by convalescent sera and post-vaccination sera Footnote 4, Footnote 5 |
July 20, 2021 |
| Omicron | B.1.1.529 and BA lineages | Evidence of increased transmissibilityFootnote 18 |
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:
- Perform enhanced genomic and case-based surveillance.
- Submit complete genome sequences and accompanying contextual data to public sequence repositories (e.g., GISAID, INSDC).
- Perform epidemiological investigations that include appropriate disaggregation by age, sex, gender, race/ethnicity, Indigeneity, socioeconomic status, and geography/place of residence as data is available to improve understanding of the potential impacts of the VOI on COVID-19 spread, severity, the effectiveness of vaccines and public health measures, or other relevant characteristics.
- Perform laboratory investigations to assess the impact of the VOI on diagnostic methods, immune responses, antibody neutralization, or other relevant characteristics.
| 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 |
| *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.
| 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 16, Footnote 17 |
October 01, 2021 |
| Lambda | C.37 | Evidence of moderate reduction in neutralization by convalescent and post-vaccine seraFootnote 23 | December 09, 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 |
February 17, 2022 |
| 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.1.1.318 |
Predicted reduction in neutralization by some monoclonal antibody therapies Predicted reduction in neutralization by polyclonal antibodies in convalescent sera |
January 27, 2022 |
| 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- Footnote 22
-
Steel, K., & Fordham, E. (2022, January 19). Coronavirus (COVID-19) Infection Survey, characteristics of people testing positive for COVID-19, UK - Office for National Statistics. Office for National Statistics.
https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/bulletins/coronaviruscovid19infectionsurveycharacteristicsofpeopletestingpositiveforcovid19uk/19january2022 - Footnote 23
-
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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