When the first case of the disease Covid-19 caused by the corona virus, SARS-CoV-2, was detected not a single person on the planet was immune to it. Finding no obstacles, the SARS-CoV-2 virus got transmitted swiftly across the globe, and WHO declared Covid-19 as a pandemic.
At present, there is not a single antiviral drug available to cure Covid-19. Scientists and researchers are making strenuous efforts, exploring every path, leaving no stone unturned to find out a vaccine that will work effectively against it. However, finding effective full proof vaccine will require months or maybe years. Scientists are also trying to find out the efficacy of already existing drugs against SARS-CoV-2 by applying drug repurposing strategy.
In today’s situation, it is very tough to anticipate anything about SARS-CoV-2. The situation is changing every day and present prediction about the disease may be wrong after a few days. The symptoms are changing, the criteria for quarantine are changing, and it is becoming difficult day-by-day to prevent the further transmission of the disease. The novel coronavirus SARS-CoV-2 is successful in giving surprises to everyone. The disease has been already spread almost in all countries across the globe. The majority of the countries are under either complete or partial lockdown, bearing the huge economic loss. The extension of lockdown may lead to a severe financial crisis as it has already disturbed the economical balance in many countries. To overcome Covid-19, a lot of attention has been diverted to a herd immunity strategy.
What is Herd Immunity?
Herd immunity is the immunity developed in the community, which protects the group of people from the infectious disease and helps to stop the spreading of the disease. It can be achieved in two ways. One method is to allow people to get contracted with the disease, build up an immune response to it and achieve natural immunity. Another method is to vaccinate a majority of the population against the disease to achieve immunity.
What is natural immunity?
When a healthy person gets contracted with the contagious disease, the human immune system stimulates the production of antibiotics against the disease-causing agents. The antibodies protect the person from the disease, and thus immunity is created against that particular infection. This is known as natural immunity. If the same person gets contracted with the same disease again, the already triggered antibodies protect the body and stop the infection.
How Herd immunity works?
There are several bacterial or viral infections, which spread through person to person contact. When a majority of the population in the community is immune to an infectious disease, the chain of disease transmission brakes and the spread of the disease automatically stop or drop drown. When such group immunity is achieved, it automatically safeguards or provides indirect protection to the people who are not vaccinated or have very low immunity. For example, if 80% of a population has achieved the immunity either by contracting the disease or by vaccination the remaining 20% who come in contact with the disease won’t get the infection or won’t spread it further. Thereby the disease spread can be kept under control. To get effective herd immunity, almost 70% to 90% of the population should get immunity. People who are prone to infections include pregnant women, babies, young children, aged people, high-risk such as diabetic or heart patients, and people with low immunity. This vulnerable group can get protection by herd immunity.
Herd Immunity and Covid-19
Herd immunity concept worked well in diseases such as measles, mumps, and swine flu when a major population was vaccinated. However, in the case of Covid-19, to date, there is no effective vaccine developed against the disease. The vaccine development and its human trials may take a longer time. Hence, for achieving herd immunity, exposing a large number of people to the disease and allowing to get contracted with the disease is the option.
The R0 (Reproduction rate) of coronavirus is roughly 2 to 2.5 in the world. That means, if one Covid infected can spread the disease to two more people. If the herd immunity to be achieved by natural immunity in the Covid-19 case, at least 70% of the population should be infected to achieve herd immunity. If 70% population is ill in any country that means the most of the people are ill. It is impossible to allow the only healthy and young population to get contracted with the disease. In addition to this if the only young population gets immunity, a large number of old population will be without immunity. Then it will require a large number of geriatric population should be kept completely under locked down condition at their homes. Without the vaccine in hand, exposing the entire population to the disease is impracticable. The mortality rate of Covid-19 is around 3.4%. If 70% of the population is infected that means a significant number of population may lose their lives due to the infection. This leads to substantial damage and suffering to society.
Why herd immunity without the support of vaccine is impractical in Covid-19 pandemic?
- If a large number of people are contracted with the disease and hospitalized, it will create huge stress on hospitals and healthcare system.
- It is not known that the immunity developed after contracting Covid-19 remains permanently, for the entire life span or just for a short period.
- Some patients with less immunity or other health problems are experiencing serious side effects. Moreover, in some serious cases, the disease is causing death.
- Scientists are not able to find out why some Covid-19 patients are asymptomatic, and why some get seriously ill while some have very mild symptoms.
- In some cases, healthy and young people who got infected are also becoming seriously ill.
Without vaccine in hand, going for herd immunity can be another kind of survival of the fittest. Until we have a highly effective vaccine which is tested and produced at a large scale, herd immunity through natural immunity seems impossible to carry out. Vaccination is required for almost everybody, including all aged people, pregnant women, infants, teens, and young adults, to get the maximum herd immunity.
Will Herd Immunity strategy work for India?
According to some researchers, herd immunity strategy could be successful in India as above 90% of the Indian population is younger than 65. In India, if the younger population is allowed to go out for work and exposed to the disease, there may be less risk of hospitalization and death. Researchers believe that allowing the virus to get released in a controlled way for the next few months would make around 60% of the country’s people immune, and thus help to halt the disease.
However, there are many hurdles in going for herd immunity strategy in India. Allowing herd immunity strategy only on the assumption that the majority of Indian population is young is very risky. A large number of young Indian population is suffering from other diseases such as diabetes, heart ailments. The majority of Covid-19 mortality cases are associated with such health problems. In many cases, it has been observed that healthy young people without any other health problem have become seriously ill or even died due to Covid-19. So it is very dangerous to expose young Indian population to the disease directly without vaccine support. If the disease becomes severe and causes deaths in a majority of the population it may lead to great damage to the country.
Until we get an effective remedy or a proven vaccine produced at a large scale, physical & social distancing, personal hygiene including frequent hand washing, is the solution to protect from SARS-CoV-2 virus. Avoid going to crowded places and try to improve self-immunity with a healthy lifestyle to protect yourself from SARS-CoV-2.
References:
- https://www.sciencealert.com/why-herd-immunity-will-not-save-us-from-the-COVID-19-pandemic
- https://www.healthline.com/health/herd-immunity
- https://www.jhsph.edu/COVID-19/articles/achieving-herd-immunity-with-covid19.html
- https://www.discovermagazine.com/health/is-herd-immunity-our-best-weapon-against-COVID-19
- https://www.technologyreview.com/2020/03/17/905244/what-is-herd-immunity-and-can-it-stop-the-coronavirus/
- https://economictimes.indiatimes.com/news/politics-and-nation/a-herd-immunity-strategy-could-actually-work-in-youthful-india/articleshow/75285241.cms?from=mdr
- https://foreignpolicy.com/2020/05/02/herd-immunity-india-coronavirus-pandemic/
