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SARS-CoV-2 immunity-escape variants
Concerns have been raised about the possible emergence of new variants that could escape the immunity induced by the vaccines. Here's a look at the recent SAGE document.
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https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/954990/s1015-sars-cov-2-immunity-escape-variants.pdf
Concerns have been raised about the possible emergence of new variants that could escape the immunity induced by the vaccines. Here's a look at the recent SAGE document.
1/10
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/954990/s1015-sars-cov-2-immunity-escape-variants.pdf
The identification of 2 new variants (B.1.1.7 in UK & B.1.351 in South Africa) with increased transmission & mutations in the Spike protein raises the theoretical risk of other variants eventually achieving "immune escape" from the current vaccines
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SARS-CoV-2 accumulates 1-2 mutation per month, which is relatively slow for an RNA virus because has proofreading capacity (can correct its own mistakes). But it's a global infection so many ppl are infected so many chances for new variants to arise. 3/10 https://academic.oup.com/ve/article/6/2/veaa061/5894560
Other concerns regarding immune escape include high community prevalence of variant B.1.1.7 and the difficult decision to delay 2nd vaccine dose to 12 weeks rather than 3 weeks
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4/10
Most mutations will have no effect, but a few confer an advantage and become dominant through natural selection (e.g. D614G noted in early Feb 2020 & became dominant global strain by June)
5/10 https://www.sciencedirect.com/science/article/pii/S0092867420315373
5/10 https://www.sciencedirect.com/science/article/pii/S0092867420315373
Lab experiments have shown it's possible to generate SARS-CoV-2 variants that are less susceptible to neutralisation by convalescent plasma
6/10 https://science.sciencemag.org/content/369/6506/1014
6/10 https://science.sciencemag.org/content/369/6506/1014
This has also been seen in an immunocompromised individual with persistent infection who was treated with convalescent plasma
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https://www.medrxiv.org/content/10.1101/2020.12.05.20241927v3
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https://www.medrxiv.org/content/10.1101/2020.12.05.20241927v3
Both vaccines in UK give higher antibody titres after 2nd doses, so theoretical risk of more viral replication after 1 dose than 2 in the short-term But in medium term, risk may be lower since delaying the 2nd Oxf vaccine dose to 12wk gave rise to 3-fold higher antibodies
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8/10
Level of antibodies after 1 dose are in range of natural infection. So 1 dose doesn't generate a new risk compared to natural infections. Risk delayed 2nd dose might generate escape mutant has to be weighed against benefits of doubling rate of vaccinating vulnerable groups
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9/10
Monitoring is key. Sequencing will determine if new clusters occur during vaccine roll out. More intense study of vaccine recipients in immunosuppressed groups is planned
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