Herd immunity and COVID-19

In this pandemic of COVID-19, we often are introduced with a term 'Herd Immunity'. Let me clear what is herd immunity. This is one kind of passive immunity in a community when majority of the infected people acquired immunity naturally or through vaccination. When 80% people get immune, then consider that rest 20% are safe from infection. In that case make sure that sufficiently large proportion (70-80%) of immune individual exist in a population.This term referred herd immunity.  After infection, body immune system start working to combat the viruses and after some days immunity can be developed or in failure, patient can be died. 

As still we don't get any vaccine, herd immunity now depends on natural immunity. Before we think to go for herd immunity, we must have to consider some important indicator which tell us how practical it is to go for herd immunity. Exact number of affected case in a certain period, Basic reproduction number, Recovery rate, Case fatality rate (death among all individuals diagnosed), Infected fatality rate (Death among infected cases), onward infection rate, Re-infection rate, nature of immunity developed (short time for 1 year or lifetime) have to be studied for herd immunity.

As the SARS-CoV-2 is a novel virus still we don't know in details the nature of the virus, it's mode of infection, the nature of immunity developed, cases of re-infection and many more things. In Bangladesh even we don't know the exact cases. New cases are increasing day by day, death rates are also increasing, we have no idea about immunity status, basic reproduction number. In this time the world is still trying to develop an effective treatment protocol. Hydroxychloroquine has temporally  banned by WHO for the treatment of COVID-19 due to high mortality. Same thing happened during the last pandemic of Spanish flu in 1918. Aspirin toxicity was occurred and took millions of life. At that time doctors suggested to take 30 grams of aspirine per day and later it was found that above 4 gram aspirin per day create toxicity. My point is before taking any decision, we have to think and rethink. Otherwise there a huge chance to do mistakes. We have to take lessons from different pandemic. 

It is very difficult to think about herd immunity in this situation when active cases are increasing and we have no vaccine to increase the number of immune people.  To establish herd immunity, onward transmission of that virus have to be prevented by natural immunity or vaccination. Pathogens which create lifelong immunity, as is the case for measles vaccination or infection, herd immunity is highly effective and can prevent pathogen spread within a population. But in case of COVID-19, reinfection and short time immunity was noticed in different countries. Moreover immune people have to be evenly distributed across the population in case of herd immunity.

We have to wait more time with patience and try to keep minimum infection rate and onward transmission. About 50 million killed in Spanish flu and 500 million peoples affected throughout the world. Vaccines comes against this disease in 1940's. Almost 90 years later in 2008, researchers discovered that a group of three genes enabled virus to weaken a victims bronchial tubes and lungs and finally the way for bacterial pneumonia, which caused the 1918 flu so deadly. Without vaccine, after 2 years in 1919 the Flu started to an ends. This pandemic gives us a lesson to wait more time to an end this deadly COVID-19. 

Science in today are more advanced, most probably the world will get a vaccine as early as possible. Scientists are trying heart and soul to develop the vaccine. We can think about herd immunity only after getting the vaccine. Till then we have to wait and maintain the regulations of WHO which prevent the spread of this virus. From the previous history of pandemic, we have to keep in mind that ' Quicker is not always better'.

Stay home, stay safe.

Nuronnabi Sagor