Abstract
Herd immunity is the most critical and essential prophylactic intervention that delivers protection against infectious diseases at both the individual and community level. This process of natural vaccination is immensely pertinent to the current context of a pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection around the globe. The conventional idea of herd immunity is based on efficient transmission of pathogens and developing natural immunity within a population. This is entirely encouraging while fighting against any disease in pandemic circumstances. A spatial community is occupied by people having variable resistance capacity against a pathogen. Protection efficacy against once very common diseases like smallpox, poliovirus or measles has been possible only because of either natural vaccination through contagious infections or expanded immunization programs among communities. This has led to achieving herd immunity in some cohorts. The microbiome plays an essential role in developing the body’s immune cells for the emerging competent vaccination process, ensuring herd immunity. Frequency of interaction among microbiota, metabolic nutrients and individual immunity preserve the degree of vaccine effectiveness against several pathogens. Microbiome symbiosis regulates pathogen transmissibility and the success of vaccination among different age groups. Imbalance of nutrients perturbs microbiota and abrogates immunity. Thus, a particular population can become vulnerable to the infection. Intestinal dysbiosis leads to environmental enteropathy (EE). As a consequence, the generation of herd immunity can either be delayed or not start in a particular cohort. Moreover, disparities of the protective response of many vaccines in developing countries outside of developed countries are due to inconsistencies of healthy microbiota among the individuals. We suggested that pan-India poliovirus vaccination program, capable of inducing herd immunity among communities for the last 30 years, may also influence the inception of natural course of heterologous immunity against SARS-CoV-2 infection. Nonetheless, this anamnestic recall is somewhat counterintuitive, as antibody generation against original antigens of SARS-CoV-2 will be subdued due to original antigenic sin.
Highlights
Herd immunity, or community immunity, is fundamentally a concept of acquiring immunity through natural infection, or mass vaccination, in a particular population
We propose that heterologous immunity is the most important factor contributing protection against SARS-CoV-2 infection in India
A few bacteria such as Parabacteroides merdae, Bacteroides stercoris, Alistipes onderdonkii and Lachnospiraceae bacterium of intestinal microbiota have the competence to reduce angiotensin-converting enzyme 2 (ACE2) expression in the gut epithelial cells, thereby influencing the calibrated immune system to encumber the pathogenicity of COVID-19
Summary
Community immunity, is fundamentally a concept of acquiring immunity through natural infection, or mass vaccination, in a particular population. Each infected person can pass the virus to two or three new people [10] This means that herd immunity should be achieved when around 60% of a particular population becomes exposed to coronavirus disease 2019. We outline several factors that can directly or indirectly alter the acquisition of immunity Among those factors, the gut microbiota is an essential element that contributes to shaping individual immunity and thereby mapping the population immunity. The robust poliovirus vaccination program developed herd immunity This same method has the ability to deliver the protection against coronavirus infection
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