UK’s herd immunity strategy to combat COVID-19

The United Kingdom (UK) has devised this novel strategy to counter the prospective damage from the novel coronavirus disease that has been declared as a pandemic by the World Health Organization (WHO). Let us take a look at the plan of action and check out if it indeed is an effective technique under the practical scenario.

 

What is meant by Herd Immunity?

As we know, our bodies have an inbuilt dynamic immune system which is capable of fighting and defending against diseases. When we recover from a particular disease the body retains an "immunological memory" of the disease which in turn allows the immune system to fight off the same ailment in future.  This is roughly how the vaccines work-they create the immunological memory without us having to "actually" contract the particular disease in the real sense.

Now the problem with a new disease, like COVID-19, we don't have such immune memory to counter the disease and no known vaccine can also be safely availed till date (ignoring the vague claims that may have occupied some pages in the news). Thus there is a good probability of the disease spreading through the population.

But this spread and the damage can be controlled if a substantially large section of the population can develop a immune memory. It is not necessary for the whole population to immediately develop immunity against the disease for such control to be effective. This is Herd immunity and has proven effective in many cases at various points of time.  

But if enough people develop an immune memory, then the disease will stop spreading, even if some of the population is not immune. This is herd immunity, and it is a very effective way to protect the whole of a population against an infectious disease.

What is the Problem?

Now the problem in the present case is that, the Herd immunity is typically effective as a prevention strategy in case of vaccination programmes. The challenge arises when we don't have a vaccine which is exactly what the present case of COVID-19 is presenting before the world. The only option is to have a significantly large portion of the population to get infected and recover from the disease to provide for such immunity.

Now, the percentage of the population that needs to be immune to enable herd immunity is dependent on the transmissibility to the disease and is measured by the term R0, 

R0 = the number of new infections each case will generate.

R0 is estimated to be 3.28 for COVID-19(even though studies are at a nascent stage and this number can vary in near future). This means that for herd immunity, about 70 per cent of the population would need to be immune to COVID-19.

To achieve Herd immunity in UK, the place of it's origin will require more than 47 million people to be infected.  Considering that COVID-19 has a 2.3 per cent case-fatality rate and a 19 per cent rate of severe disease it would easily lead to more than a million deaths and 8 million severe cases in the country alone.

For a country like India where the population is way more than that in the UK, it is likely to cause huge death toll.  Besides the availability to quality healthcare, especially to the deprived sections of the society is severely limited in India.

So, Now What?

The National Health Service in UK is probably planning to implement a delayed spread of infection through the population so as to not overwhelm the health facilities in the country.  While it may be of limited significance in a country like UK with low density of population and a well-established and extremely functional healthcare system, it would be utter chaos and may have an extremely dangerous outcome for the people, if tried in India. Therefore, it is a better strategy to prevent the novel coronavirus spread altogether than risk countering it head-on.

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