|LETTER TO EDITOR
|Year : 2022 | Volume
| Issue : 1 | Page : 83-84
SARS-CoV-2 variants of concern - An emerging global threat
P Charulata Sree1, Venkata Ramana Kandi2, Tarun Kumar Suvvari3
1 Rungta College of Dental Sciences and Research, Chhattisgarh, India
2 Department of Microbiology, Prathima Institute of Medical Sciences, Karimnagar, Telangana, India
3 Dr. NTR University of Health Sciences, Vijayawada, Andhra Pradesh, India
|Date of Submission||10-Sep-2021|
|Date of Decision||17-Oct-2021|
|Date of Acceptance||04-Nov-2021|
|Date of Web Publication||04-Jan-2022|
Mr. Tarun Kumar Suvvari
Dr. NTR University of Health Sciences, Vijayawada, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sree P C, Kandi VR, Suvvari TK. SARS-CoV-2 variants of concern - An emerging global threat. Indian J Respir Care 2022;11:83-4
|How to cite this URL:|
Sree P C, Kandi VR, Suvvari TK. SARS-CoV-2 variants of concern - An emerging global threat. Indian J Respir Care [serial online] 2022 [cited 2022 Jan 26];11:83-4. Available from: http://www.ijrc.in/text.asp?2022/11/1/83/334803
India's first wave of COVID-19 was relatively mild when compared to the second wave and was controlled by a nationwide lockdown. However, the B.1.1.7 variant (Alpha), introduced by travel from the United Kingdom (UK) in late 2020, spread rapidly in the country and was known to be more transmissible than previous virus bearing the D614G spike mutation. Its variant B.1.617.2 later renamed as “Delta” emerged in India during late 2020 and early 2021. Later, the Delta variant underwent some more genetic variations to evolve into B.1. 617.3. The Delta variants quickly held a spot among one of several “variants of concern” as designated by the Centers for Disease Control and Prevention and WHO by spreading rapidly across the country and possessing a certain threat to places where vaccination rates remained low. The key to the Delta-driven resurgence is the collection of mutations; the variant has accumulated in its spike protein making existing antibodies difficult to bind as tightly or as often. Some synthetic antibodies such as bamlanivimab were unable to neutralize the Delta variant while others including etesivimab, casirivimab, and imdevimab were still considered effective. Since the Delta variants have shown resistance to treatment with convalescent plasma and neutralizing monoclonal antibodies, and because there is emerging evidence of re-infections among the vaccinated population with the Delta variants, the efficacy of vaccines, and the protection they offer to the vaccinated people remains to be completely understood.
Tim spector, a genetic epidemiologist at King's College London who is leading a “COVID symptom study,” has reported that the common symptoms of COVID have shown a slight change with headaches, sore throat, and runny nose among most frequently reported symptoms rather than fever, cough, and loss of smell since the variant prevailed through the country. This could delay the suspicion and diagnosis because people suffering from seasonal flu show similar symptoms. Above data have not been peer-reviewed and published in any scientific journal and some scientists remain unconvinced. Angela Rasmussen, a virologist at the Vaccine and Infectious Disease Organization at the University of Saskatchewan said that a milder symptom profile can be blamed for the variant showing infection primarily in younger people who are less likely to be vaccinated or people who have already been exposed to the virus.
As compared to its previous circulating lineages, Delta variant is considered 1.1–1.4-fold more transmissible and better able to evade immunity elicited by previous infection. Reports suggest that the variant was 5.7-fold less sensitive to neutralizing antibodies acquired from sera of previously infected individuals. It showed a higher replication in human primary airway cells justifying its high transmissibility rate. B.1.617.2 was marginally less sensitive to the TMPRSS2 inhibitor camostat suggesting an enhanced entry efficiency into the receptors.
In a study, the Delta variant live virus was isolated to test susceptibility to vaccine elicited neutralizing antibodies in individuals vaccinated with ChAdOx-1 (Covidshield/AstraZeneca) or BNT162b2 (Pfizer–BioNTech). The results showed a loss of sensitivity for Delta variant, and the mean GMT against Delta Variant spike PV was lower for ChAdOx-1 as compared to BNT162b2.
Effectiveness after one dose of either one of the vaccines mentioned above with Delta variant was notably lower as compared to alpha. Effectiveness after two doses of BNT162b2 vaccine was reported to be 88% while it was 67% with ChAdOx1 nCoV-19 vaccine. Mutations at P681 in the PBCS have been observed in multiple SARS-CoV-2 lineages, more specifically in the B.1.1.7 Alpha variant showing significantly higher fusogenic potential; i.e., demonstrating a higher fusion activity and syncytium formation. During the experimentation of postvaccine sera and its potential to block syncytia formation, Delta variant could permit cell–cell fusion in the respiratory tract with higher pathogenicity even among vaccinated individuals with neutralizing antibodies. Alarmed by the reduced efficacy against the Delta variant, companies including the one producing BNT162b2 have started to think of a booster dose while announcing that they have developed an updated version specifically targeting the Delta variant. These combined epidemiological and in vitro data suggested that the predominance of the Delta variant in India could be due to union of evasion of neutralizing antibodies in previously infected individuals and increased virus infectivity.
In conclusion, Delta's arrival alerted the whole scientific community about the potential of SARS-CoV-2 mutations and its drastic consequences. Until a vaccine is developed showing exceptional results regarding the mutant variant, continuing with public health intervention should be considered critical. As a vaccine can only slow down the progression of a contagious disease by increasing herd immunity, preventive measures such as social distancing and masking are of utmost importance for curbing the spread of the virus.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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