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expert reaction to latest figures for cases of variants of concern (VOCs) and under investigation (VUIs) and technical briefings on variants of concern published by PHE

Public Health England (PHE) has released more data on the Delta variant first detected in India (B.1.617.2).


Dr Julian Tang, Honorary Associate Professor/Clinical Virologist, Respiratory Sciences, University of Leicester, said:

“The latest data on the delta (Indian B.1.617.2) variant shows what we expected to some extent – that the main focus of these infections is in the under 30s who have not been extensively vaccinated yet. There is as yet no convincing evidence of more severe disease, though the predominance of the delta variant over the previous alpha variant now, confirms an increased transmissibility over this earlier variant – and a much higher transmissibility over the original Wuhan virus.

“So although about 10% of hospitalised cases of the delta variant seem to be in those who have had 2 vaccine doses, this is well within the 80-90% range of protection conferred after 2 doses of vaccine.

“As a consequence of the ongoing COVID-19 vaccination programme into the younger age groups, this will drive the virus into the under-18 child age-range, so in the absence of current COVID-19 vaccination in this age group, the virus will eventually concentrate in this school-age population which will eventually become a reservoir and driver of any ensuing delta variant epidemic, as well as being a hotspot in which new mutations may arise.

“The acquisition of the K417N in the delta-AY.1 variant is a worrying development, as we know that this mutation is found in the South African (beta, B.1.351) variant that has enhanced transmissibility as well as significant vaccine escape properties. It is likely that this K417N mutation together with the L452R mutation present in the all the Indian variants (also seen in the Californian CAL.20C/B.1.427/B.1.429 epsilon variant) may enhance the delta-AY.1’s vaccine escape properties.

“Relaxing restrictions further with this potentially highly transmissible delta-AY.1 variant with potentially even more effective vaccine escape properties, with about a 10% hospitalisation rate even in those who have had 2 doses of vaccine, will be a concern as we enter the 2021 winter season – especially if seasonal influenza and other respiratory viruses return as COVID-19 restrictions are removed.”



Variants: distribution of case data, 11 June 2021

Investigation of SARS-CoV-2 variants of concern: technical briefings



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