Finding a medicine or vaccine for the novel COVID is of paramount importance in every country right now, but the recurring failure is forcing people to consider other ways to deal with the current threat. That other immunity seeking method considered is herd immunity.
Before jumping into what herd immunity is, let’s clear the concept of how immunity or treatment against pathogens or vaccination works.
Why do we get sick and eventually recover?
When a pathogen infects the body, the leucocytes recognize the pathogen and produce the necessary antibody to fight the pathogen. The number of leucocytes or commonly known as white blood cells present in a human body ranges from 4000- 11,000 per microliter of blood. But for pathogens that are new, like Coronavirus causing COVID-19, are previously not registered and not recognized by the white blood cells. Hence the sudden sickness and late recovery. For some pathogens, the antibody produced during one sickness can live as long as an entire lifetime and prevent the recurrence of the disease, for example, chickenpox.
Immunity is basically strengthening these white blood cells and increasing their number, similar to setting up an army to prevent breach by enemies.
Vaccination uses the same theory to ensure protection. A weak version of the pathogen(known as antigen) is introduced to the body to instigate the production of antibodies such that the virus is not a surprise to the body. But in the case of COVID-19, a failure to procure vaccine has led to the consideration of Herd Immunity.
What is herd immunity?
After measuring the reproduction number of a pathogen(how many people can the patient infect on average), mortality rate, mode of transmission, and serial interval, one can determine the herd immunity threshold of that disease.
A disease that infects a large group of people due to a high reproduction number or easy methods of transmission will affect larger and larger crowds each day till it runs out of ‘infectible’ people because most of them have already been naturally vaccinated by getting infected once. Although many diseases including measles, mumps, and smallpox was dealt with herd immunization which has the herd immunity threshold of 86% (smallpox) of the population, it isn’t suitable for every disease.
Why is herd immunity perhaps unsuitable for the COVID-19 pandemic?
Longevity of the vaccination- Some antibodies stay active for as long as a lifetime. But scientists so far do not know how long the antibody for the COVID-19 virus would be active, making the question of herd immunity uncertain.
Mutation- Some viruses like the Influenza virus is mutated to a level that even after the initial vaccine shot, the people are advised yearly shot to prevent infection by the virus. After a few mutations, this particular Coronavirus causing COVID-19 could be like the Influenza virus that can have sturdier survival chances.
A dangerous strategy- Although the strategy has proven to be a success earlier, there is no proof it could be successful for the current pandemic. Without any drug or way to control the virus, allowing the disease to spread so as to ensure herd immunity is risky.
What is the herd immunity threshold for Coronavirus? Unlike smallpox or other diseases, the herd immunity threshold has not been determined for COVID-19 yet. Although it is normally between 60-90% of the population, it’s still a vague percentage to depend on before taking the huge decision.
The herd- This immunity is only achievable for a stagnant herd of people. Traveling, migrating, relocating can jeopardize the entire process and restart an infection in a new group. Hence in a country where many people work abroad or in different cities, movement is unwelcome for the success of the agenda.
The percentage required- The world has a population of 7.8 billion. And so far 7.8 million people have been infected by the virus. That is a negligible percentage and definitely not enough for the herd immunity that is being aimed for.
Hence, herd immunization may not be a very smart choice for dealing with COVID-19.