HERD IMMUNITY — Is It the Panacea?
It’s been more than a year since COVID-19 was introduced in our life, and It has changed the way we live, forever. With the emergence of this virus, parallel talks have been started about the importance of herd immunity. Different people have different understanding of what herd immunity is and how it helps in fighting a pandemic. So let’s take a moment and understand what herd immunity is and what the fuss is all about.
What is Herd Immunity?
Herd immunity against an infectious disease is achieved when enough people have developed immunity to the disease– either through a previous infection or vaccination –and it becomes difficult for the disease to spread rapidly. Thus, it provides indirect protection even for those who don’t have immunity to the disease yet.
Depending on the infection rate of the disease, a minimum percentage of the population must develop the immunity before it is safe to say that herd immunity is reached.
Herd Immunity Threshold for Covid-19
Herd immunity threshold is the percentage of the population that needs to be immune to prevent a disease’s spread. More contagious the disease, the higher the threshold. For example, in case of measles, 95% of a population must have immunity to measles to prevent continued disease transmission. But there is a caveat here. Even after the population, as a whole, has obtained herd immunity, local outbreaks are still very plausible. Experts have estimated that 70–90% of the population needs to be vaccinated in order to curb ever rising COVID-19 infection.
Currently in India, two indigenous vaccines and few from other parts of the world are in the roll out stage and showing promising results. However, if a new strain can dodge the body’s immune response, that will dampen the nation’s effort at achieving herd immunity and that has been the biggest fear since the various mutant strains have hit the nation.
Does Herd Immunity mean back to normal?
Another big question we all wonder, does herd immunity mean back to normal as was before pandemic? And the answer is not likely because the virus will continue to circulate even after the herd immunity threshold will reach. For example in a scenario in which herd immunity is achieved and an average sick person infects 0.8 other people, which means that now 100,000 people would go on to infect 80,000 more and so on.
Maintaining herd immunity is a constant battle so as in other infectious diseases since the virus keeps on evolving to evade immune response. That’s why the flu vaccine is administered every year. This was the very reason for the measles outbreak in 2019 when vaccination rate went down in certain communities.
Is Herd Immunity a False God?
There is no certainty about how long immunity to SARS-CoV-2 lasts. Experts believe it to be 6–8 months and it is likely that additional vaccination will be needed to prime the immune system.
While increasing the number of vaccinations is important, herd immunity has become somewhat of a False God. In reality, what should be of more concern is the number of cases, hospitalization and deaths in a community and if those numbers are going down, it doesn’t matter if the number of people vaccinated in a community is 5% or 55%.
We can be “in and out” of herd immunity but our behavior as a society of masked and socially distanced people will surely get us through these tough times we are living in.
