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Living Evidence - SARS-CoV-2 variants

Living evidence tables provide high level summaries of key studies and evidence on a particular topic, and links to sources. They are reviewed regularly and updated as new evidence and information is published.

Viruses constantly change through mutation and over time, new variants of a virus are expected to occur. Some variants have characteristics that have a significant impact on transmissibility, severity of disease and effectiveness of vaccines.  This table includes information on variants that are currently causing concern in the scientific community.

Currently, the World Health Organization  has identified four variants of concern: Alpha, Beta, Gamma and Delta.

Daily checks are conducted for new content and any updates that occur during the week are highlighted. All highlights are removed each Monday.

Alpha (B.1.1.7) Beta (B.1.351) Gamma (B.1.1.28.1 (P.1) Delta (B.1.617.2)
WHO label Alpha Beta Gamma Delta
Scientific names

B.1.1.7

GRY (formerly GR/501Y.V1)

20I/S:501Y.V1

Variant of Concern (VOC) - 202012/01

B.1.351

GH/501Y.V2

20H/S:501Y.V2

Variant of Concern (VOC) – 202012/02

B.1.1.28.1 (P.1)

GR/501Y.V3

20J/S:501Y.V3

Variant of Concern (VOC) – 202101/02

B.1.617.2

G/452.V3

21A/S:478K

Variant of Concern (VOC) - VOC-21APR-02

First detected

UK

September 2020

South Africa

May 2020

Brazil

November 2020

India

October 2020

Mutations 23 (17 of which change amino acids)

Includes N501Y substitution

21 (8 of which change amino acids)

Includes N501Y substitution

17 (11 of which change amino acids)

Includes N501Y substitution

12

Includes spike mutation profiles L452R, E484Q and D614G and lacks mutations at amino acid positions 501 or 484 in its ACE2 receptor.

Delta-AY.1 (Delta with K417N)

Transmissibility compared with wild type

Reproduction number (Ro) ~3.5-5.2*^

Increased transmissibility and secondary attack rate compared with wild type*^

Estimated 25.1% secondary attack rate compared with 20.2% for wild type

Estimated 43–90% higher reproduction number than wild type and transmission advantage at warmer temperatures *^

Estimated high seroprevalence rate in secondary school-aged children*^ and some studies inferring an increase in within-school transmission*^

Increased transmissibility and estimated to be 2.5 times greater than wild type*^

Increased transmissibility and secondary attack rate compared with wild type^

Reproduction number (Ro) ~5.5-6.5

Increased transmissibility and secondary attack rate compared with wild type*^

Estimated transmission equivalent to Alpha and 50% - 60 % higher than wild typewith a doubling time between  3.5-16 days*^

Estimated 42% secondary attack rate*^ and increased household transmission compared to Alpha*^

Estimated increase in cases involving primary and secondary school settings*^

Estimated detection can be 4 days after exposure compared with six days for wild type*^

Virulence/severity or duration of disease compared with wild type

Increased risk of hospitalisation, possible increased risk of severity including a greater requirement for supplemental oxygen and mechanical ventilation, and possible increased risk of mortality*^  (including low-risk groups*^)

However, there is conflicting evidence: some studies suggest no association between severe disease and death*, symptoms or disease burden*^

Average infections last 13.3 days compared with 8.2 days for other variants*^ and Alpha does not appear to influence patient trajectories including onset to hospitalisation and length of stay*^

Estimated increased risk of in-hospital mortality*^

Estimated increased risk of hospitalisation and possible increased risk of severity and deaths among populations without pre-existing diseases*^

Resistant against Bamlanivimab*^ and efficiently inhibited by Etesevimab, Imdevimab and by Casirivimab/Imdevimab*^

Estimated viral load ~1000 times higher than other strains*^

Emerging evidence to suggest symptoms can differ to wild type*^

Immune escape (vaccines / previous infections will not be protective)
Pfizer/BioNTech (BNT162b2)

Estimated <2-fold reduction in neutralisation*^

Full vaccination (≥7 days after dose 2) up to 89% vaccine effectiveness against symptomatic infection*^

Estimated effectiveness from other studies up to 93%*^

Reduced vaccine effectiveness under different dosage and timing conditions*^, notably lower after one dose*^

Estimated 5 to <10-fold reduction in neutralisation*^

Full vaccination (≥7 days after dose 2) up to 84% vaccine effectiveness against symptomatic infection*^

Reduced vaccine effectiveness under different dosage and timing conditions*^

Neutralisation increased with prior COVID-19 infection*^

Estimated 2 to <5-fold reduction in neutralisation

Full vaccination (≥7 days after dose 2) up to 84% vaccine effectiveness against symptomatic infection*^

Neutralisation increased with prior COVID-19 infection*^

Estimated 5 to <10-fold reduction in neutralisation with some studies suggesting a 11.30-fold reduction^*

Full vaccination (≥7 days after dose 2) up to 87% vaccine effectiveness against symptomatic infection^*

Estimated effectiveness from other studies is up to 92%*^

Reduced vaccine effectiveness under different dosage and timing conditions, notably lower after one dose*^

Reports that Pfizer Inc. plans to ask regulators to authorise a booster dose*^ and also develop a vaccine to target Delta*^ following reported drops in vaccine effectiveness*^ Reports Israel is providing a third dose for people with immunodeficiency*^

AstraZeneca (AZD1222)

Estimated 5 to <10-fold reduction in neutralisation*^

Vaccination (≥14 days after dose 1 only) up to 64% vaccine effectiveness against symptomatic infection*^

Other studies suggest 66% to 74.6% effectiveness for prevention of symptomatic disease*^

Reduced vaccine effectiveness under different dosage and timing conditions*^, notably lower after one dose*^

Estimated 5 to <10-fold reduction in neutralisation*^

Vaccination (≥14 days after 1 dose only) up to 48% vaccine effectiveness against symptomatic infection*^

Other studies suggest 10.4% effectiveness for prevention of symptomatic disease*^

Estimated 2 to <5-fold reduction in neutralisation*^

Vaccination (≥14 days after dose 1 only) up to 48% vaccine effectiveness against symptomatic infection*^

Reports of effectiveness for prevention of symptomatic disease (news reporting on preliminary data)*^

Estimated 2 to <5-fold reduction in neutralisation*^

Vaccination (≥14 days after one dose only) up to 67%  vaccine effectiveness against symptomatic infection*^

Reduced vaccine effectiveness under different dosage and timing conditions*^, notably lower after one dose*^

Moderna (mRNA-1273)

Estimated <2-fold reduction in neutralisation*^

Full vaccination (≥7 days after dose 2) up to 92% vaccine effectiveness against symptomatic infection*^

Estimated 5 to <10-fold reduction in neutralisation*^

Vaccination (≥14 days after dose 1 only) up to 77% vaccine effectiveness against symptomatic infection*^

Estimated 2 to <5-fold reduction in neutralisation*^

Vaccination (≥14 days after dose 1 only) up to 77% vaccine effectiveness against symptomatic infection*^

Estimated 2 to <5-fold reduction in neutralisation*^

Vaccination (≥14 days after dose 1 only) up to 72% vaccine effectiveness against symptomatic infection*^

Novavax

Estimated 86% vaccine effectiveness for prevention of symptomatic disease*^ with one study suggesting  89.7% protection after two doses*^

Estimated  ≥10-fold reduction in neutralisation*^

Estimated vaccine effectiveness for moderate to severe disease (52% ≥14 days and 64% ≥28 days) and for severe to critical disease (73.1% ≥14 days and 81.7% after ≥28 days*^

  
Johnson & Johnson (Ad26.COV2.S)Estimated 2 to <5-fold reduction in neutralisation*^

≥10-fold reduction in neutralisation*^

Estimated 85% vaccine effectiveness for prevention of symptomatic disease *^

Estimated 2 to <5-fold reduction in neutralisation*^

Estimated  <2-fold reduction in neutralisation^*

Sputnik V Gam-COVID-Vac 

Estimated 5 to <10-fold reduction in neutralisation*^

  
Immune escape - other

Elicits cross-reactive neutralising antibodies*

Sinovac-CoronaVac: significant reduction in neutralising antibody capacity compared to wild type*^

Elicits cross-reactive neutralising antibodies^

Bharat-Covaxin (BBV152): neutralisation with an estimated 3-fold reduction*^

Sinovac-CoronaVac: significant reduction in neutralising antibody capacity compared to wild type*^

Elicits cross-reactive neutralising antibodies^

Sinovac-CoronaVac: estimated <2-fold reduction in neutralisation and a reduction in vaccine effectiveness*^

Cases of reinfection with an estimated 6.4% reinfection probability*^

Spread is associated with an escape to antibodies targeting non-RBD and RBD Spike epitopes*^

Bharat-Covaxin (BBV152): estimated 2.7 fold reduction in neutralisation, 65.2% vaccine effectiveness including disease severity and mortality*^

Estimated higher protection following a previous infection and Covishield doses, with Covishield effective in preventing disease severity and morality*^

Estimated to escape adaptive immunity induced by prior wild type infection around half the time*^

Reports that prior COVID-19 infections results in less severe disease against subsequent infection*^

Reports of breakthrough infections*^  and early evidence suggesting full vaccination can reduce breakthrough cases and if infected reduce  risk of  risk of hospitalisation*^

Testing and detection

PCR effective at detecting and distinguishing variant*^

Lateral flow devices effective in detecting*^

Wastewater-based SARS-CoV-2 sequencing effective in detecting variants*^

Multiple studies report reliable assays for rapid detection of variants.^

PCR effective at

detecting variant*^

Wastewater-based SARS-CoV-2 sequencing effective in detecting variants*^

Multiple studies report reliable assays for rapid detection of variants.^

PCR effective at

detecting variant*^

Wastewater-based SARS-CoV-2 sequencing effective in detecting variants*^

Multiple studies report reliable assays for rapid detection of variants.^

Estimated to be effective in detecting and quantifying variant*^

Lateral flow devices effective in detecting*^

Links with post-acute COVID-19 syndrome Not established Not established Not established Not established.
Countries reporting detection (not necessarily local transmission) Detected in ~155 countries

Previously the dominant strain in UK (now Delta) and the second most common variant found in India*^
Detected in ~105 countries

Dominant strain in South Africa
Detected in ~68 countries

Dominant strain in Brazil        

Detected in ~104 countries

Dominant strain in India, USA, the UK and other countries including Australia

The World Health Organization (WHO) announced the Variant naming system  on 1 June 2021. The labels do not replace existing scientific names. Designations include Variant of Interest (VOI) and Variant of Concern (VOC).  A previously designated VOI or VOC can also be reclassified if it no longer pose a major added risk to global public health.

WHO has provided a working definition for ‘Alerts for Further Monitoring’; for a Variant with genetic changes that are suspected to affect virus characteristics with some indication that it may pose a future risk, but evidence of phenotypic or epidemiological impact is unclear.

Details are tabulated when Variants meet the World Health Organization (WHO) definition of Variant of Concern:

  • Increase in transmissibility or detrimental change in COVID-10 epidemiology; or
  • Increase in virulence or change in clinical disease presentation; or
  • Decrease in effectiveness of public health and social measures or available diagnostics, vaccines and therapeutics.

Reports of Variants of Interest (VOI) are updates identified in the grey literature are below:

Notes

*Preliminary data, not fully established, in some cases small numbers or short follow up; interpret with caution

^ Commentary grey literature, pre peer review or news

Background

Evidence check - SARS-CoV-2 variants (PDF)

Living evidence tables include some links to low quality sources and an assessment of the original source has not been undertaken. Sources are monitored daily but due to rapidly emerging information, tables may not always reflect the most current evidence. The tables are not peer reviewed, and inclusion does not imply official recommendation nor endorsement of NSW Health.

Last updated on 26 Jul 2021

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