What is Herd Immunity actually?

When the majority of the population becomes immune to infectious disease, indirect protection is formed for those who are not immune to the disease. This is known as herd immunity or herd protection.

For example, if 80% of the population is immune to viruses, then 4 out of 5 people who come across the disease won’t be sick. They won’t spread the disease further. Thus, the spread of disease can be controlled. Generally, 70% – 90% of the population needs immunity for achieving herd immunity.

How it works

Herd Immunity can work in two ways –

  1. The people who contract the disease will build an immune response which is a natural immunity
  2. The people can be vaccinated for achieving immunity.

We should know, that about 380 Trillion viruses are residing in an average human body. Not all are harmful or dangerous. About 38 Trillion bacteria inhabit our human body. Viruses are found inside and outside the human body. Sometimes, healthy bacteria play an important role in preventing pathogen intrusion.

Viral and bacterial infections spread from one person to another. This chain is stopped when the majority of the people don’t contract or transmit the infection.

This in turn protects those who are not vaccinated or have low immunity. Viruses like the flu mutate over time. Therefore, antibodies from early infection protect for a brief period. SARS-CoV-2 is a virus that causes COVID-19. Those who have immunity against it can be estimated to have immunity from months to years. This doesn’t mean it will be forever.

Who are vulnerable to infections and diseases?

These can include –

  1. Senior citizens
  2. Babies
  3. People with weak immune systems
  4. Pregnant women
  5. Young children
  6. People with health conditions


UK Prime Minister, Boris Johnson talks about herd immunity

Why herd immunity and people’s favor of it?

Once measles, mumps, chickenpox, and polio were very common in the US. Due to hard immunity, it’s now very rare in the US. Outbreaks of vaccines are seen in communities that have lower vaccine access. This is due to the absence of herd protection.

Leaders like Boris Johnson, the prime minister of the United Kingdom suggest that it might be a preferable way to fight against COVID-19 infection.

Sweden is open and didn’t take a strict lockdown measure. The Swedish government has issued guidelines for Swedes. These include staying at homes and closing museums. However, schools, restaurants, and parks are virtually open. In May, Sweden’s ambassador to the US, Karin Ulrika Olofsdotter stated that Stockholm (Sweden’s capital) can reach herd immunity within that month.


What will it take to achieve herd immunity for SARS-CoV-2?

As of the early estimates of this virus’s infectiousness, at least 70% of the population needs to be immunity for herd protection.

In the worst-case scenario, a lack of physical distancing will infect many people within a few months. This would be devastating to the health care system. Hospitals and clinics will be full resulting in a high death rate.

In the best-case scenario, the continual efforts of social distancing can be maintained for an extensive period of a year or more before a highly effective vaccine is developed and mass distributed. This is with the maintenance of current levels of infection.

The most likely cause is that infection rates will rise and fall with time. We may relax these measures when the infection rate falls. Then again, we can re-implement measures as the infection rate increases. However, it is unlikely that we will see this explosive outburst of cases like now. Most people will develop immunity in the future.

Many scientists are against the idea of herd immunity for fighting COVID-19. This is because the concept is developed for the creation of vaccines where there is no risk of death.
At the bottom line, it will take further time to make the situation get better. Strict social distancing measures and guidelines will play a more active role than herd immunity for preventing COVID-19.

See also :


The author studied from CSE at Military Institute of Science and Technology

Author : Farhan Sadeed

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