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Placing the Delta ‘Plus’ variant (AY.4.2) under the microscope

08 Nov 2021

By Buddhika Samaraweera More than 22 months have passed since the outbreak of the Coronavirus Disease-2019 (Covid-19), which has affected more than 250 million individuals worldwide and caused over 5 million deaths. However, given the appearance of new SARS-CoV-2  variants, which are reported from time to time, how long would it take to eradicate this pandemic is still a serious matter. The World Health Organisation (WHO) has divided the variants of the SARS-CoV-2 into two main categories; variants of concern (VOC) and the variants of interest (VOI). Accordingly the variants such as the Alpha (B.1.1.7), Beta (B.1.351), Delta (B.1.617.2), and Gamma (P.1), have been designated as VOC while the variants such as Eta (B.1.525), Iota (B.1.526), Kappa (B.1.617.1), Mu (B.1.621), and Lambda (C.37) have been designated as VOI. The latest variant of SARS-CoV-2 – the Delta “Plus” or the AY.4.2 variant has been reported in many countries as of present. London Institute of Immunity and Transplantation and Health Services Laboratories Professor and Consultant in Clinical Immunology and Allergy Prof. Suranjith L. Seneviratne shared with The Morning the latest findings about the Delta “Plus” Covid-19 variant. What is the Delta “Plus” variant? Viruses multiply and spread from cell to cell and person to person. During the process of multiplication, changes may occur in the genetic make-up of the virus. The SARS-CoV-2 Delta variant has continued to evolve and pick up mutations. Such mutations have produced different sub-lineages of Delta, and AY.4.2 is one such sub-lineage. Currently, AY.4.2 is classified as a variant under investigation (VUI) by the UK Health Security Agency (UKHSA). In contrast, the Delta variant is classified as a VOC. A variant is designated as a VOC, when there is evidence of fulfilling at least one of several criteria; an increase in transmissibility, more severe disease (such as increased hospitalisations or deaths), significant reduction in neutralisation by antibodies that are produced during a previous SARS-CoV-2 infection or vaccination, failures with diagnostic testing, or reduced effectiveness of treatments or vaccines. The SARS-CoV-2 virus uses the spike protein to enter our cells. AY.4.2 has two characteristic mutations (Y145H and A222V) in the spike protein of SARS-CoV-2. The mutations are in a part of the spike protein that is frequently recognised and targeted by antibodies. The Y145H and A222Y mutations have previously been found in other coronavirus lineages. However, these two mutations have not been found in any of the current VOC. The A222V change was found in the B.1.7.7 lineage that spread in Europe in the summer of 2020. Currently where is the Delta “Plus” variant found? So far, AY4.2 has been reported in 36 countries across the world. Most cases (that is 28,667) have been identified in the UK, with 21,158 cases found in England. In the week up to 27 October, 7,521 more people were infected with the AY.4.2 variant in the UK. This is the latest time period for which data is available. During this same period, there were 57,411 new reported cases of the Delta variant. The number of cases of Delta “Plus” in some other countries include: Germany – 379 cases, Denmark – 304 cases, and Poland – 159 cases. It has also been reported from the US, Israel, Ireland, and Russia. At present, its frequency in India remains low. Currently in the UK, the Delta variant still accounts for most of the Covid-19 cases, but the proportion of the Delta “Plus” variant appears to be increasing. Is the Delta “Plus” variant more transmissible? There is some early evidence that the Delta “Plus” variant may have an increased transmission rate compared to the Delta variant. Several experts state it is around 10% more transmissible than the Delta variant of coronavirus. The Delta variant was 60% more transmissible than the Alpha variant. The Delta “Plus” variant’s secondary attack rate (the probability of an infection occurring in a group of people) is around 12.4% for a household in the UK. For the Delta variant, it is 11.1%. Thus, there is a greater chance of infection spreading within a household if one person is infected with Delta “Plus”. As the incubation period is shorter with the Delta “Plus” variant, it can be transmitted faster and spread more easily than the Delta variant does. Does the Delta “Plus” variant cause more severe disease? As yet, there is no evidence that it causes a more severe illness. The UKHSA has recently stated that AY4.2 does not appear to be causing more severe disease. However, any significant increase in cases could lead to higher numbers of persons with serious disease and thus more hospitalisations. Is vaccine or disease immunity effective against the Delta “Plus” variant? The current vaccines are effective in protecting against hospitalisation and death due to Covid-19, and are effective against the currently circulating variants. Information available so far suggests the existing vaccines are effective against Delta “Plus” and would continue to protect people effectively.


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