Abstract

The emergence of the NB.1.8.1 variant of COVID-19 in India marks another critical juncture in the ongoing trajectory of the pandemic. A progeny of the Omicron BA.2.86 lineage, NB.1.8.1 harbours multiple mutations in the spike protein, particularly in the receptor-binding domain(RBD), like F486P, E484K, N501Y, which raise concerns about increased infectivity and potential immune escape. Although it has not been designated a Variant of Concern by the World Health Organisation (WHO), its genetic profile warrants close monitoring. Clinically, the variant primarily presents with mild upper respiratory and systemic symptoms; however, high-risk individuals remain vulnerable to complications. Current diagnostic modalities, including RT-PCR and antigen-based assays, remain effective, while genomic surveillance is essential for accurate variant detection. Early reports suggest no increase in severity; however, high transmissibility of the NB.1.8.1 variant could still place significant strain on healthcare systems. Vaccination continues to provide strong protection against severe illness, though booster uptake remains suboptimal, particularly among the elderly and immunocompromised patients. While reinfection is possible, hybrid immunity and T-cell-mediated response offer a degree of protection. As NB.1.8.1 spreads, India must respond with scientific vigilance rather than complacency by strengthening surveillance, updating vaccines, reinforcing public health measures, and maintaining community awareness. Adaptive, evidence-based strategies are urgently required to address the dynamic mutational landscape of the SARSCoV-2 virus.

• 1.   https://timesofindia.indiatimes.com/ toireporter/author-toi-news-desk-479263436. cms. [Accessed on: May 20, 2025]
• 2.   Aden D., Zaheer S., Kumar R., Raj S., Khan T., Varshney S. Beyond COVID-19 and SARSCoV-2, cardiovascular outcomes of “long COVID” from a pathological perspective - a look back and road ahead. Pathol Res Pract. 2022 Nov; 239: 154144. doi: 10.1016/j. prp.2022.154144
• 3.   SARS-CoV-2 variants of concern as of 25 April 2025 https://www.ecdc.europa.eu/en/ covid-19/variants-concern [Accessed on: May 20 ,2025]
• 4.   https://dbtindia.gov.in/insacog [Accessed on May 25,2025]
• 5.   WHO TAG-VE Risk Evaluation for SARS-CoV-2 Variant Under Monitoring: NB.1.8.1.1.8.1. https://cdn.who.int/media/docs/defaultsource/documents/epp/tracking-sarscov-2/23052025_nb.1.8. [Accessed on: May 22, 2025]
• 6.   Tracking SARS-CoV-2 variants. https://www. who.int/activities/tracking-SARS-CoV-2- variants. [Accessed on: May 25 ,2025]
• 7.   h t t p s : / / w w w . t i m e s n o w n e w s . c o m / india/273-cases-in-kerala-in-may-23-in-delhicovid-19-cases-surge-across-india-experts-sayrise-not-a-worry-article-151709665. [Accessed on May 20 ,2025]
• 8.   https://news.abplive.com/health/covidupdate-nb181-lf7-variants-found-in-indiaamid-surge-scare-1-death-reported-inthane-1774705. [Accessed on: May 25 ,2025]
• 9.   No need to panic over new Covid variant, precautions still key: Doctors. https://www. tribuneindia.com/news/delhi/no-need-topanic-over-new-covid-variant-precautionsstill-key-doctors. [Accessed on: May 26, 2025]
• 10.   Should you be worried about Covid variant JN.1? Check what doctors are saying. https:// economictimes.indiatimes.com/news/newupdates/should-you-be-worry-about-jn-1- heres-what-doctors-are-saying-regardingnew-covid-variant/articleshow/121390309. cms?from=mdr. [Accessed on: May 26, 2025]
• 11.   Park G.W., Reija B., Tamin A., Hicks H., Flanders M.H., Metz J.M., et al. Comparative analysis of environmental persistence of SARSCoV-2 variants and seasonal coronaviruses. Appl Environ Microbiol. 2025 Apr 23; 91(4): e0168824. Doi: 10.1128/aem.01688-24
• 12.   https://economictimes.indiatimes.com/ news/international/global-trends/newcovid-variant-nb-1-8-1-detected-at-usairports-amid-rise-in-cases-check-forsymptoms-and-preventive. [Accessed on: May 24, 2025]
• 13.   New Covid variant NB.1.8.1 detected at US airports amid rise in cases. Check for symptoms and preventive measures
• 14.   New Covid variant NB.1.8.1 detected at US airports amid rise in cases. Check for symptoms and preventive measures. https:// economictimes.indiatimes.com/news/ international/ global-trends/new-covidvariant-nb-1-8-1-detected-at-us-airportsamid-rise-in-cases-check-for-symptoms-andpreventive measures/articleshow/ 121380180. cms? From = mdr. [Accessed on: May 23, 2025]
• 15.   h t t p s : / / c d n . w h o . i n t / m e d i a / d o c s / default-source/documents/epp/trackings a r s - c o v - 2 / 2 3 0 5 2 0 2 5 _ n b . 1 . 8 . 1 _ i r e . pdf?sfvrsn=7b14df58_4. [Accessed on: May 24, 2025]
• 16.   Xue S., Han Y., Wu F., Wang Q. Mutations in the SARS-CoV-2 spike receptor binding domain and their delicate balance between ACE2 affinity and antibody evasion. Protein Cell. 2024 May 28;15(6):403-418. doi: 10.1093/ procel/pwae007.
• 17.   Zabidi N.Z., Liew H.L., Farouk I.A., Puniyamurti A., Yip A.J.W., Wijesinghe V.N., et al. Evolution of SARS-CoV-2 Variants: Implications on Immune Escape, Vaccination, Therapeutic and Diagnostic Strategies. Viruses. 2023 Apr 10; 15(4): 944. doi: 10.3390/ v15040944.
• 18.   Aden D., Zaheer S. Investigating the FLiRT variants of COVID-19: Is it an emerging concern? Pathol Res Pract. 2024 Oct;262:155542. doi: 10.1016/j.prp.2024.155542.
• 19.   World Health Organiza on Tracking SARSCoV-2 Variants Available online: h ps:// www.who.int/ac vi es/trackingSARS-CoV-2- var1iants [Accessed on: May 24, 2025]
• 20.   Pather S., Charpentier N., van den Ouweland F., Rizzi R., Finlayson A., Salisch N., et al. Benefit- Risk Assessment of VAccines by TechnolOgy Working Group (BRAVATO; ex-V3SWG). A Brighton Collaboration standardized template with key considerations for a benefit-risk assessment for the Comirnaty COVID-19 mRNA vaccine. Vaccine. 2024 Sep 17; 42(22): 126165. doi: 10.1016/j.vaccine.2024.126165.
• 21.   New Covid variant NB.1.8.1 detected at US airports amid rise in cases. Check for symptoms and preventive measures. https://m.economictimes.com/news/ international/global-trends/new-covid137 IJPRP / Volume 15 Number 2 May – August 2026 variant-nb-1-8-1-detected-at-us-airportsamid-rise-in-cases-check-for-symptoms-andpreventive-measures/articleshow/121380180. cms. [Accessed on: May 25, 2025]
• 22.   https://m.economictimes.com/news/india/ new-covid-nb-1-8-1-and-lf-7-subvariantsdetected-in-india-as-cases-tick-up-in-pockets/ articleshow/121377974.cms. [Accessed on: May 24, 2025]
• 23.   Jamie Ducharme. What to Know About the ‘FLiRT’ Variants of COVID-19. https://time. com/6972143/covid-19-FLiRT-variants-kp-2/. [Accessed on: May 24, 2025]
• 24.   Carabelli A.M., Peacock T.P., Thorne L.G., Harvey W.T., Hughes J.; COVID-19 Genomics UK Consortium; Peacock S.J., Barclay WS, de Silva T.I., Towers G.J., Robertson D.L. SARSCoV-2 variant biology: immune escape, transmission and fitness. Nat Rev Microbiol. 2023 Mar; 21(3): 162-177. doi: 10.1038/s41579- 022-00841-7.
• 25.   h t t p s : / / w w w . o n l y m y h e a l t h . c o m / symptoms-of-new-covid-variants-nb181-andlf7-12977831770. [Accessed on: May
• 27.   Koyama A.K., Siegel D.A., Oyegun E., Hampton W., Maddox N., Koumans E.H.. Symptoms Reported With New Onset of Loss of Taste or Smell in Individuals With and Without SARSCoV-2 Infection. JAMA Otolaryngol Head Neck Surg. 2021 Oct 1;147(10):911-914. doi: 10.1001/jamaoto.2021.2239.
• 28.   Adly H.M., Saleh S.A.K., Garout M.A., Abdulkhaliq A.A., Khafagy A.A., Saati A.A. Post COVID-19 Symptoms Among Infected Vaccinated Individuals: A Cross-Sectional Study in Saudi Arabia. J Epidemiol Glob Health. 2023 Dec; 13(4): 740-750. doi: 10.1007/ s44197-023-00146-9
• 29.   https://m.economictimes.com/news/ new-updates/nb-1-8-1-lf-7-variants-ofcovid-detected-in-india-check-if-its-deadlysymptoms-preventive-measures-otherdetails-covid-news/articleshow/121391901. [Accessed on: May 26, 2025]
• 30.   h t t p s : / / w w w . l i v e m i n t . c o m / n e w s / india/most-covid-19-infections-mildhealth-ministry-urges-vigilance-as-newvariant-jn-1-detected-all-you-need-toknow-11748137753450.html . [Accessed on: May 24, 2025]
• 31.   Lamba S., Ganesan S., Daroch N., Paul K., Joshi S.G., Sreenivas D. et al. SARS-CoV-2 infection dynamics and genomic surveillance to detect variants in wastewater - a longitudinal study in Bengaluru, India. Lancet Reg Health Southeast Asia. 2023 Apr; 11: 100151. doi: 10.1016/j. lansea.2023.100151. 32. Jian F., Yisimayi A., Song W., Wang J., Xu Y., Chen X et al. Humoral immunogenicity comparison of XBB and JN.1 in human infections. bioRxiv 2024.04.19.590276. doi: 10.1101/2024.04.19.590276.
• 33.   India detects cases of new NB.1.8.1 and LF.7 COVID strains; experts say no need to panic. https://www.newindianexpress.com/ nation/2025/May/25/india-detects-cases-ofnew-nb181-and-lf7-covid-strains-experts-sayno-need-to-panic. [Accessed on: May 26, 2025].
• 34.   https://www.cdc.gov/covid/long-termeffects/index.html. [Accessed on: May 26, 2025]
• 35.   Centers for Disease Control and Prevention (CDC). Seasonal Influenza and COVID-19: Considerations for Health Systems. https:// www.cdc.gov. [Accessed on: May 26, 2025].
• 36.   World Health Organization (WHO). Risk Communication and Community Engagement for Influenza and COVID-19. https://www.who. int. [Accessed on: May 26, 2025].
• 37.   https://www.thehindu.com/sci-tech/health/ whats-behind-the-recent-covid-19-spike-inindia/article69605844. [Accessed on: May 25, 2025].
• 38.   https://idsp.mohfw.gov.in/. [Accessed on: May 26, 2025].
• 39.   https://www.aninews.in/news/national/ general-news/delhi-government-issuesadvisory-to-hospitals-amid-rising-covid-19- cases20250523222229Refresher training for staff should be conducted. [Accessed on: May 26, 2025].
• 40.   https://www.cdc.gov/coronavirus/2019- ncov/symptoms-testing/testing.html. [Accessed on: May 26, 2025].
• 41.   Shahid S., Parveen S., Vyas N., Abuhasaballah H.H.A., Annadurai S., El Assadi S.A. et al. Tracking of SARS-CoV-2 Variants of Concern by RT-PCR Assay in the Post-Pandemic Era. New Emirates Medical Journal. 2024; 5: Volume 5, 0250-6882. doi: 10.2174/0102506882 268552230922112521.
• 42.   Lerner A.M., Folkers G.K., Fauci AS. Preventing the Spread of SARS-CoV-2 With Masks and Other “Low-tech” Interventions. JAMA. 2020; 324(19): 1935–1936. doi:10.1001/ jama.2020.21946
• 43.   Aden D., Zaheer S., Raj S. Challenges faced in the cancer diagnosis and managementCOVID-19 pandemic and beyond-Lessons for future. Heliyon. 2022 Dec 5; 8(12). doi: 10.1016/j.heliyon.2022.e12091 44. https://www.cdc.gov/clean-hands/about/ hand-sanitizer.html. [Accessed on: May 26, 2025] Durre Aden, Nadeem Ahmad, Sufian Zaheer. Vigilance, Not Panic: Understanding the Emerging COVID-19 Variant NB.1.8.1.138 Indian Journal of Pathology: Research and Practics IJPRP / Volume 15 Number 2 May – August 2026 .
• 45.   https://www.nhs.uk/conditions/covid-19/ covid-19-symptoms-and-what-to-do/ Avoid unnecessary gatherings, especially for vulnerable individuals during periods of increased viral activity. [Accessed on: May 26, 2025] .
• 46.   https://www.cdc.gov/infection-control/ hcp/isolation-precautions/precautions.htm. [Accessed on: May 26, 2025] .
• 47.   Aden D., Zaheer S., Kumar R, Ranga S. Monkeypox (Mpox) outbreak during COVID-19 pandemic-Past and the future. J Med Virol. 2023 Apr; 95(4)doi: 10.1002/ jmv.28701.
• 48.   h t t p s : / / w w w . w h o . i n t / e m e r g e n c i e s / diseases/novel-coronavirus-2019/advice-forpublic. [Accessed on: May 26, 2025]
• 49.   Menegale F., Manica M., Zardini A., et al. Evaluation of Waning of SARS-CoV-2 Vaccine–Induced Immunity: A Systematic Review and Meta-analysis. JAMA Netw Open. 2023; 6(5): e2310650. doi:10.1001/ jamanetworkopen.2023.10650
• 50.   Shete A.M., Patil D.Y., Sahay R.R., Sapkal G.N., Deshpande G.R., Yadav P.D. Waning natural and vaccine-induced immunity leading to reinfection with SARS-CoV-2 Omicron variant. Hum Vaccin Immunother. 2022 Nov 30; 18(6): 2127289. doi: 10.1080/21645515.2022.2127289.
• 51.   Khoury D.S., Schlub T.E., Cromer D., Steain M., Fong Y., Gilbert P.B., et al. Correlates of Protection, Thresholds of Protection, and Immunobridging among Persons with SARSCoV-2 Infection. Emerg Infect Dis. 2023 Feb; 29(2): 381-388. doi: 10.3201/eid2902.221422
• 52.   Murhekar M.V., Bhatnagar T., Thangaraj J.W.V., Saravanakumar V., Kumar M.S., Selvaraju S., ICMR Sero surveillance Group. SARS-CoV-2 seroprevalence among the general population and healthcare workers in India, December 2020-January 2021. Int J Infect Dis. 2021 Jul; 108: 145-155. doi: 10.1016/j. ijid.2021.05.040.
• 53.   Khan, K., Lustig, G., Römer, C. et al. Evolution and neutralization escape of the SARS-CoV-2 BA.2.86 subvariant. Nat Commun 14, 8078 (2023). https://doi.org/10.1038/s41467-023- 43703-3
• 54.   Bergeri I., Whelan M.G., Ware H., Subissi L., Nardone A., Lewis H.C. Global SARS-CoV-2 seroprevalence from January 2020 to April 2022: A systematic review and meta-analysis of standardized population-based studies. PLoS Med. 2022 Nov 10; 19(11): e1004107. doi: 10.1371/journal.pmed.1004107.
• 55.   Tarke A., Coelho C.H., Zhang Z., Dan J.M., Yu E.D., et al. SARS-CoV-2 vaccination induces immunological T cell memory able to crossrecognize variants from Alpha to Omicron. Cell. 2022 Mar 3; 185(5): 847-859.e11. doi: 10.1016/j.cell.2022.01.015.
• 56.   Keeton, R., Tincho, M.B., Ngomti, A. et al. T cell responses to SARS-CoV-2 spike crossrecognize Omicron. Nature. 2022 603: 488–492. doi: 10.1038/s41586-022-04460-3
• 57.   Lau J.J., Cheng SMS, Leung K., Lee C.K., Hachim A., Tsang LCH, Real-world COVID-19 vaccine effectiveness against the Omicron BA.2 variant in a SARS-CoV-2 infection-naive population. Nat Med. 2023 Feb; 29(2): 348-357. doi: 10.1038/s41591-023-02219-5.
• 58.   Mukhopadhyay L., Gupta N., Yadav P.D., Aggarwal N. Neutralization assays for SARS-CoV-2: Implications for assessment of protective efficacy of COVID-19 vaccines. Indian J Med Res. 2022 Jan; 155(1): 105-122. doi: 10.4103/ijmr.ijmr_2544_21.
• 59.   Sharma N., Basu S., Lalwani H., Rao S., Malik M., Garg S. COVID-19 Booster Dose Coverage and Hesitancy among Older Adults in an Urban Slum and Resettlement Colony in Delhi, India. Vaccines (Basel). 2023 Jun 29; 11(7): 1177. doi: 10.3390/vaccines11071177
• 60.   Rizvi A.A., Singh A. Vaccination coverage among older adults: A population-based study in India. Bull World Health Organ. 2022 Jun 1; 100(6): 375-384. doi: 10.2471/BLT.21.287390.
• 61.   Das S., Kar S.S., Samanta S., Banerjee J., Giri B., Dash S.K. Immunogenic and reactogenic efficacy of Covaxin and Covishield: A comparative review. Immunol Res. 2022 Jun; 70(3): 289-315. doi: 10.1007/s12026-022-09265- 0. Epub 2022 Feb 22.
• 62.   Mahumud R.A., Ali M.A., Kundu S., Rahman M.A., Kamara J.K., Renzaho A.M.N. Effectiveness of COVID-19 Vaccines against Delta Variant (B.1.617.2): A Meta-Analysis. Vaccines (Basel). 2022 Feb 11; 10(2): 277. doi: 10.3390/vaccines10020277.
• 63.   Zhou Z., Zhu Y., Chu M. Role of COVID-19 Vaccines in SARS-CoV-2 Variants. Front Immunol. 2022 May 20; 13: 898192. doi: 10.3389/fimmu.2022.898192
• 64.   Shanti Pather, Nicola Charpentier, Frank van den Ouweland, Ruben Rizzi, Andrew Finlayson, et al. A Brighton Collaboration standardized template with key considerations for a benefit-risk assessment for the Comirnaty COVID-19 mRNA Vaccine,Volume 42, Issue 22,2024
• 65.   Ella R., Reddy S., Jogdand H., Sarangi V., Ganneru B., Prasad S. et al. Safety and immunogenicity of an inactivated SARSCoV-2 vaccine, BBV152: interim results from a double-blind, randomised, multicentre, phase 2 trial, and 3-month follow-up of a doubleblind, randomised phase 1 trial. Lancet Infect139 IJPRP / Volume 15 Number 2 May – August 2026 Dis. 2021 Jul; 21(7): 950-961. doi: 10.1016/ S1473-3099(21)00070-0.
• 66.   Tobias J., Steinberger P., Wilkinson J., Klais G., Kundi M., Wiedermann U. SARS-CoV-2 Vaccines: The Advantage of Mucosal Vaccine Delivery and Local Immunity. Vaccines (Basel). 2024 Jul 18; 12(7): 795. doi: 10.3390/ vaccines12070795.
• 67.   Ministry of Health and Family Welfare, Government of India. Operational Guidelines for COVID-19 Preparedness and Response in India. 2024 https://www.mohfw.gov.in. [Accessed on: May 26, 2025]. 68. Centers for Disease Control and Prevention (CDC). (2024). Interim Clinical Considerations for Use of COVID-19 Vaccines. h t t p s : / / w w w . c d c . g o v / v a c c i n e s / covid-19/clinical-considerations/interimconsiderations-us.html. [Accessed on: May 26, 2025].
• 69.   Yang, J., Rai, K.K., Alfred, T. et al. The impact of COVID vaccination on incidence of long COVID and healthcare resource utilisation in a primary care cohort in England, 2021–2022. BMC Infect Dis 25, 214 (2025). doi: 10.1186/ s12879-024-10097-6
• 70.   Català M., Mercadé-Besora N., Kolde R., Trinh N.T.H., Roel E., Burn E., Rathod-Mistry T., et al. The effectiveness of COVID-19 vaccines to prevent long COVID symptoms: staggered cohort study of data from the UK, Spain, and Estonia. Lancet Respir Med. 2024 Mar; 12(3): 225-236. doi: 10.1016/S2213-2600(23)00414-9.
• 71.   Centres for Disease Control and Prevention. February 1, 2024. COVID Data Tracker. Centres for Disease Control and Prevention. May 11, 2024. [Accessed on: May 26, 2025]
• 72.   Soukhovolsky V., Kovalev A., Pitt A, Shulman K., Tarasova O., Kessel B. The Cyclicity of coronavirus cases: “Waves” and the “weekend effect”. Chaos Solitons Fractals. 2021 Mar; 144: 110718. doi: 10.1016/j.chaos.2021.110718. Epub 2021 Jan 28.
• 73.   Filip R., Gheorghita Puscaselu R, AnchidinNorocel L., Dimian M., Savage W.K. Global Challenges to Public Health Care Systems during the COVID-19 Pandemic: A Review of Pandemic Measures and Problems. J Pers Med. 2022 Aug 7; 12(8): 1295. doi: 10.3390/ jpm12081295

Data Sharing Statement

Funding