#16,040
The Delta variant, first detected in India and now embarked on its world tour, has demonstrated its increased transmissibility every place it has landed, but its other attributes are less clear cut.
There is some evidence that it may increase hospitalizations, that it may evade previously acquired immunity, and that it may render some vaccines less effective. But how significant these traits are remain unknown.
The CDC's SARS-CoV-2 Variant Classifications and Definitions page describes Delta as:
B.1.617.2 (Pango lineage)a
Spike Protein Substitutions: T19R, (G142D*), 156del, 157del, R158G, L452R, T478K, D614G, P681R, D950N
Name (Nextstrain)b: 20A/S:478K
WHO Label: Delta
First Identified: India
Attributes:
- Increased transmissibility 29
- Potential reduction in neutralization by some EUA monoclonal antibody treatments 7, 14
- Potential reduction in neutralization by post-vaccination sera 21
Other than increased transmissibility, the remaining attributes remain murky. In an attempt to better understand the risks posed by the Delta variant, a multi-national collaboration of research scientists have published a new paper in the journal CELL, which attempts to identify and quantify Delta's antibody escape abilities.
The good news is, most vaccines appear to offer protection against the Delta variant - albeit not as robust as against older `wild-type' COVID - but comparable to the protection they offer against the Alpha and Gamma variants.We've a link and excerpt from the journal pre-proof, along with a media release from FIOCRUZ, which was one of the research organizations involved.
While vaccines remain protective, it is likely the rate of `breakthrough' infections among the vaccinated will be higher with these three variants.
The researchers did find that immunity among those previously infected with COVID to be less protective against the Delta variant. This lack of immunity was most apparent (11-fold reduction) in those previously infected with the Gamma (P.1) or Beta (B.1.351) variants.
For those hoping that a previous bout and recovery from COVID will protect them against future infection, this isn't exactly reassuring news. Vaccine recipients, while not 100% protected, appear far more resistant to infection.
First stop, excerpts from the summary from FIOCRUZ.
Research suggests increased risk of reinfection by the Delta variant
06/28/2021
Maíra Menezes (IOC/Fiocruz)
A recently published study with the participation of the Oswaldo Cruz Foundation (Fiocruz) suggests that the Delta variant of the new coronavirus, initially detected in India, may increase the risk of reinfections. Research shows that serum from people previously infected with other strains is less potent against this viral variant. The problem is markedly observed among individuals previously infected by the Gamma variant, originally identified in Manaus and currently dominant in Brazil, as well as by the Beta variant, first detected in South Africa. In these cases, the ability to neutralize the strain Delta is eleven times smaller.
Serum from vaccinated people also has reduced potency against the Indian-originated variant, but data show that the vaccines remain effective. The ability to neutralize the strain is 2.5 times lower for Pfizer's immunizing agent and 4.3 times lower for Astrazeneca's. The authors of the work emphasize that the indices are similar to those verified with the Gamma and Alpha variants – which emerged in Brazil and the United Kingdom, respectively. There is no evidence of widespread avoidance of neutralization, unlike that recorded with the Beta variant – originating in South Africa.
“It seems likely from these results that current RNA and viral vector vaccines will provide protection against the B.1.617 strain [which has three sublineages, including the Delta variant], although an increase in infections may occur as a result of the ability to reduced serum neutralization,” the researchers state in the article.
This is a lengthy (74-page) and highly detailed PDF file, and so I've only hit the highlights. Follow the link to read it in its entirety.
Reduced neutralization of SARS-CoV-2 B.1.617 by vaccine and convalescent serum
Chang Liu, Helen M. Ginn, Wanwisa Dejnirattisai, Piyada Supasa, Beibei Wang, Aekkachai Tuekprakhon, Rungtiwa Nutalai, Daming Zhou, Alexander J. Mentzer, Yuguang Zhao, Helen M.E. Duyvesteyn, César López-Camacho, Jose Slon-Campos, Thomas S. Walter, Donal Skelly, Sile Ann Johnson, Thomas G. Ritter, Chris Mason, Sue Ann Costa Clemens, Felipe Gomes Naveca, Valdinete Nascimento, Fernanda Nascimento, Cristiano Fernandes da Costa, Paola Cristina Resende, Alex PauvolidCorrea, Marilda M. Siqueira, Christina Dold, Nigel Temperton, Tao Dong, Andrew J. Pollard, Julian C. Knight, Derrick Crook, Teresa Lambe, Elizabeth Clutterbuck, Sagida Bibi, Amy Flaxman, Mustapha Bittaye, Sandra Belij-Rammerstorfer, Sarah C. Gilbert, Tariq Malik, Miles W. Carroll, Paul Klenerman, Eleanor Barnes, Susanna J. Dunachie, Vicky Baillie, Natali Serafin, Zanele Ditse, Kelly Da Silva, Neil G. Paterson, Mark A. Williams, David R. Hall, Shabir Madhi, Marta C. Nunes, Philip Goulder, Elizabeth E. Fry, Juthathip Mongkolsapaya, Jingshan Ren, David I. Stuart, Gavin R. Screaton
Received 25 May 2021, Revised 4 June 2021, Accepted 11 June 2021, Available online 17 June 2021.
Highlights
• Vaccine/convalescent sera show reduced neutralization of B.1.617.1 and B.1.617.2• Sera from B.1.351 and P.1 show markedly reduced neutralization of B.1.617.2• B.1.351, P.1 and B.1.617.2 are antigenically divergent• Vaccines based on B.1.1.7 may broadly protect against current variants
Summary
SARS-CoV-2 has undergone progressive change with variants conferring advantage rapidly becoming dominant lineages e.g. B.1.617. With apparent increased transmissibility variant B.1.617.2 has contributed to the current wave of infection ravaging the Indian subcontinent and has been designated a variant of concern in the UK.Here we study the ability of monoclonal antibodies, convalescent and vaccine sera to neutralize B.1.617.1 and B.1.617.2 and complement this with structural analyses of Fab/RBD complexes and map the antigenic space of current variants. Neutralization of both viruses is reduced when compared with ancestral Wuhan related strains but there is no evidence of widespread antibody escape as seen with B.1.351.However, B.1.351 and P.1 sera showed markedly more reduction in neutralization of B.1.617.2 suggesting that individuals previously infected by these variants may be more susceptible to reinfection by B.1.617.2. This observation provides important new insight for immunisation policy with future variant vaccines in non-immune populations.
