COVID-19 vaccines vs the Delta variant: How effective are they?
COVID-19 Vaccines Delta variant

COVID-19 vaccines vs the Delta variant: How effective are they?

Santhni Subramaniam
Santhni Subramaniam

In 10 seconds? Current Covid-19 vaccines’ efficacy is lower against the rapidly spreading Delta variant than previous strains, researchers suggested.

What have researchers discovered? In a pre-print published study (not peer-reviewed by third-party scientists), the predicted efficacy of the Moderna jab against infection by the Delta variant was found to be 71.4%, i.e 20% lower than against earlier ‘prototype’ viral strains. The AstraZeneca-Oxford vaccine fared even worse: offering 50% less protection at only 27.5%. (see Column A in the chart below) The team has also analyzed protection offered against symptomatic disease caused by the Delta variant offering a somewhat better protection (Column B in the chart). However, when comparing severe Covid-19 caused by the Delta variant, the Moderna vaccines provided almost 100% protection, Pfizer was estimated to provide 75.3% protection while Johnson&Johnson’s efficacy was predicted at 56.9%.

Comparison of predicted efficacy against ‘Reference lineages’(blue) and the Delta variant (purple) across (a) SARS-CoV-2 infection, (b) symptomatic Covid-19, and (c) Severe Covid-19.  mrna-1273=Moderna, ChAdOx1 nCoV-19=AstraZeneca, bnt162b2=PfizerBioNTech, Ad26.cov2=Johnson & Johnson. Source: Chen, et al 2021.
Comparison of predicted efficacy against ‘Reference lineages’(blue) and the Delta variant (purple) across (a) SARS-CoV-2 infection, (b) symptomatic Covid-19, and (c) Severe Covid-19.

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