Contents

Some variants of concern

SARS-CoV-2 infects cells and forces them to produce copies of this virus. Small errors, or mutations, in the production of copies of SARS-CoV-2 occur from time to time. These mutations result in a slightly altered shape or structure of the virus. Over many cycles of infection, as the virus passes from one person to another, mutations accumulate. Mutations that confer an advantage to the virus tend to be carried forward in future copies of the virus. Mutant viruses that can increase harm in some way—such as causing infection more easily, evading the immune system’s defences, and so on—are called variants of concern (VOC) by scientists.

Variants of concern tend to have at least one of the following issues:

  • they are more easily spread
  • they have the potential to cause more severe COVID-19
  • they may be able to escape from natural immunity; that is, people who have previously been infected with the virus and recovered may become infected in the future
  • they may be able to escape from vaccine-induced immunity or antibody-based treatments

Selected variants of concern

Information on variants of concern is constantly evolving. For the most recent information about variants of concern in your region, speak to your local public health authorities.

Also, the U.S. Centers for Disease and Control (CDC) has some information on variants of concern at the link below:

https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/variant-surveillance/variant-info.html

In the case of the following variants of concern, comparisons are made to the original variant of SARS-CoV-2 that appeared in late 2019. These comparisons are largely based on test-tube studies:

  • B.1.1.7 – this variant has 23 mutations and was first identified in the UK in December 2020. It is about 50% more transmissible and may have caused more severe COVID-19 in some people. According to the CDC, it likely has a “minimal” impact on the effectiveness of antibodies generated by vaccination and on antibody-based therapies.
  • B.1.351 – this variant has 23 mutations and was initially reported in South Africa in December 2020. It is about 50% more easily spread and, according to the CDC, it has “modest” impact on most vaccines and some antibody-based therapies. However, data from South Africa suggests that it can have a significant impact on protection from the AstraZeneca vaccine, reducing its effectiveness.
  • P1 – this variant has 35 mutations and was initially reported in Brazil in January 2021. According to the CDC, it has a “moderate” impact on some antibody therapies and on antibodies generated by the Pfizer-BioNTech and Moderna vaccines.

These variants are spreading and have been reported in many countries, including Canada.

Other VOC include the following:

  • B.1.427 and B.1.429 – these variants that were first isolated in California are estimated by the CDC to be about 20% more transmissible than the original strain of SARS-CoV-2. Furthermore, they can significantly reduce the effectiveness of some antibody-based therapies and “modestly” reduce the effectiveness of vaccines.

Over time, it is likely that other VOC will appear around the world.

Cellular immunity

Note that the previous assessments about vaccines and variants are based largely on antibodies. The minimal level of antibodies needed in the body for protection against SARS-CoV-2 (and variants) after vaccination is not known.

Most vaccines stimulate B-cells to produce antibodies that attack a target – in this case, part of SARS-CoV-2 or a cell infected with this virus. However, vaccines also stimulate T-cells (and likely other cells of the immune system, such as natural killer cells) to recognize virus-infected cells and, as a consequence, release antiviral substances as they attack and destroy these cells. This is called cellular immunity. This type of immunity can also be helpful against SARS-CoV-2. Cellular immunity arising from vaccination has generally not been thoroughly assessed against many VOC at the time this publication went to press. At any rate, the rise and spread of VOC means that it is crucial for pharmaceutical companies to develop vaccines that are effective against a broad range of variants. Such research is now underway.

—Sean R. Hosein

Resources

Government of Canada – https://health-infobase.canada.ca/covid-19/epidemiological-summary-covid-19-cases.html#VOC

U.S. Centers for Disease Control and Prevention – https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/variant-surveillance/variant-info.html

British Columbia Centres for Disease Control – http://www.bccdc.ca/health-info/diseases-conditions/covid-19/about-covid-19/variants

Institut national de santé publique du Québec – https://www.inspq.qc.ca/covid-19/labo/variants ; https://www.inspq.qc.ca/nouvelles/variants-du-sras-cov-2-pourquoi-s-en-preoccuper ; https://www.inspq.qc.ca/covid-19/donnees/variants

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