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Year : 2021  |  Volume : 2  |  Issue : 1  |  Page : 48-49

Is herd immunity for COVID-19 a promising strategy for India?

Department of Community and Family Medicine, All India Institute of Medical Sciences, Rishikesh, Uttarakhand, India

Date of Submission15-May-2020
Date of Decision30-Jun-2020
Date of Acceptance18-Nov-2020
Date of Web Publication25-Apr-2021

Correspondence Address:
Dr. Meenakshi Khapre
Department of Community and Family Medicine, All India Institute of Medical Sciences, Rishikesh - 249 203, Uttarakhand
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JME.JME_53_20

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How to cite this article:
Sinha S, Sharma A, Khapre M. Is herd immunity for COVID-19 a promising strategy for India?. J Med Evid 2021;2:48-9

How to cite this URL:
Sinha S, Sharma A, Khapre M. Is herd immunity for COVID-19 a promising strategy for India?. J Med Evid [serial online] 2021 [cited 2022 Sep 30];2:48-9. Available from: http://www.journaljme.org/text.asp?2021/2/1/48/314632

With a global upsurge in the cases of coronavirus disease 2019 (COVID-19), the number has gone above ten million cases worldwide as of 18 July 2020.[1] According to the Union Ministry of Health, the case toll in India has gone above one million as of 18 July 2020.[2] India is witnessing a rise in the cases of COVID-19 caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). Initially, India was able to maintain a 'steady phase' in its spread. Since April 1st week, despite the strict lockdown and containment strategy adopted by the Government of India, the number of cases is on the rise. If we look at the state-level data, some of the states are performing really well, whereas others are struggling to control the spread of infection. The emergence of SARS-CoV-2 led to the pandemic because it was a novel virus for which populations across the world are susceptible. Any infectious disease, when introduced into a susceptible population, tends to spread rapidly because most of the people in populations are prone to be infected. Thus, to put a halt on the exponential spread of the infection and to bring down the epidemic curve, the number of immune individuals has to be increased. The immune individuals provide protection to susceptible people due to indirect effect, termed herd immunity. To understand what proportion of these individuals are required to achieve herd immunity, it is important to understand R0.[3],[4] R0 refers to the average number of secondary infections caused by a single infectious individual introduced into a completely susceptible population. A comparison of 12 studies reported that R0 for COVID-19 ranges from 1.5 to 6.68. The mean and median values of R0 for COVID-19 were found to be 3.28 and 2.79, respectively.[5],[6] The day-to-day data on COVID-19 depict a wide range of differences in the number of cases and the growth rate. The median value of growth rate during the first, second, third and fourth phases of lockdown was reported to be 13.74, 6.88, 5.58 and 4.88, respectively.[7] At present, R0 for SARS-CoV-2 in India is 1.22 by analysis of the disease progression as reported by the Institute of Mathematical Sciences, Chennai, on 16 June 2020. Considering the best estimate of R0 for COVID-19 as 3 as reported by studies, the proportion of Immune individuals in India has to be at least 67% (for R0 = 3, we have ν [herd immunity threshold] =1 − 1/3 × 100 = 67%).[8] It means 70% of the population has to be infected to achieve herd immunity. Applying this proportion to India in terms of numbers will have a huge number of cases.[1],[9] Besides, diseases such as diabetes, ischaemic heart disease, chronic obstructive pulmonary disease, stroke and hypertension attribute the major causes of disability-adjusted life years in India.[10] All these have the potential to adversely affect the outcome of COVID-19. Apart from many unknowns about SARS-CoV-2, a critical point to consider is that it is a novel virus with very limited knowledge of how it affects the human immune system or how long the immunity lasts? The idea of attaining herd immunity to SARS-CoV-2, in the absence of any vaccine, can overwhelm the already-burdened health-care infrastructure during a pandemic by allowing a significant fraction of the population to become infected deliberately. This effect will be especially devastating for countries where hospitals have limited surge capacity, where public health infrastructure is not robust. Thus, aiming for achieving herd immunity by getting exposed to infection could be detrimental for India with a high burden of morbid conditions and limited health resources.[11],[12] Kapoor et al. estimated that India has approximately 1.9 million hospital beds, 95,000 intensive care unit beds and 48,000 ventilators.[13] Moreover, we must appraise that herd immunity by natural infections is a consequence of an epidemic. It should not be the strategy to control it.. As the epidemic advances, R0 is bound to decrease by itself and will fall below 1. We must aim to achieve herd immunity by vaccination, and not by disease. However, as evidence across the globe suggests, herd immunity by vaccination is not possible until next year, therefore the prime focus should be on strategies such as hand hygiene, social distancing and public health measures such as strengthening contact tracing and surveillance. A collective effort is required from health as well as travel, transport, economics, security and other sectors until the time vaccine is made available.[9],[13],[14] Thus, to conclude, in the context of SARS-CoV-2, whose epidemiology is complex and still under evolution with unavailability of vaccines, establishing herd immunity should not be the ultimate goal. Instead, guidelines and policies to contain the disease transmission and vulnerable groups should be given emphasis. After an effective vaccine for SARS-CoV-2 is approved, the phenomenon of herd immunity might be taken as a primary objective, which can be achieved through global immunisation programmes with high vaccine coverage and strict surveillance. However, at present, the concept of herd immunity in relation to COVID-19 appears more to be theoretical, which might have detrimental effects. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.

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MoHFW. Government of India. COVID-19 India. Available from: https://www.mohfw.gov.in/. [Last accessed on 2020 Jun 19].  Back to cited text no. 2
CDC. Vaccine Glossary of Terms. CDC; 2019. Available from: https://www.cdc.gov/vaccines/terms/glossary.html. [Last accessed on 2020 May 11].  Back to cited text no. 3
Fine P, Eames K, Heymann DL. Herd immunity: A rough guide. Clin Infect Dis 2011;52:911-6.  Back to cited text no. 4
Kwok KO, Lai F, Wei WI, Wong SY, Tang JW. Herd immunity – Estimating the level required to halt the COVID-19 epidemics in affected countries. J Infect. 2020; 80:e32–e33.  Back to cited text no. 5
Liu Y, Gayle AA, Wilder-Smith A, Rocklöv J. The reproductive number of COVID-19 is higher compared to SARS coronavirus. Travel Med 2020; 27:taaa021.  Back to cited text no. 6
Ghosh K, Sengupta N, Manna D, De SK. Inter-state transmissionpotential and vulnerability of COVID-19 in India. Prog Disaster Sci. 2020;7:100114.  Back to cited text no. 7
Julia C, Nadia A. Spread-of-Disease. Available from: https://calculate.org.au/wp-content/uploads/sites/15/2018/10/spread-of-disease.pdf. [Last accessed on 2020 May 12].  Back to cited text no. 8
D'souza G, Dowdy D. What is herd immunity and how can we achieve it with COVID-19? Johns Hopkins Bloomberg School Public Health. 2020. Available from: https://www.jhsph.edu/covid-19/articles/achieving-herd-immunity-with-covid19.html. [Last accessed on 2020 May 11].  Back to cited text no. 9
Indian Council of Medical Research, Public health Foundation of India, Institute of Health Metric and Evaluation. India: Health of the Nation's States the India State-Level Disease Burden Initiative. New Delhi, India: ICMR, PFHI and IHME; 2017. Available from: https://www.healthdata.org/sites/default/files/files/policy_report/2017/India_Health_of_the_Nation%27s_States_Report_2017.pdf. [Last acessed on 2020 Jul 18].  Back to cited text no. 10
Jose AP, Prabhakaran D. World hypertension day: Contemporary issues faced in India. Indian J Med Res 2019;149:567-70.  Back to cited text no. 11
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IDF Diabetes Atlas 9th Edition 2019. Available from: https://diabetesatlas.org/en/. [Last accessed on 2020 May 15].  Back to cited text no. 12
Güner R, Hasanoğlu I, Aktaş F. COVID-19: Prevention and control measures in community Turk J Med Sci 2020;50:571-7.  Back to cited text no. 13
Dowdy D, D'souza G. Early Herd Immunity against COVID-19: A Dangerous Misconception. Johns Hopkins Coronavirus Resource Center. Available from: https://coronavirus.jhu.edu/from-our-experts/early-herd-immunity-against-covid-19-a-dangerous-misconception. [Last accessed on 2020 May 11].  Back to cited text no. 14


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