As the world continues to battle the COVID-19 infection with mass vaccination and strict virus-related restrictions, many of us are keen to know what the process is yielding and when will the world reach ‘herd immunity. This discussion often poses a very important question- what proportion of the population will need to be vaccinated in order to reach herd immunity?

This is not a simple question to answer, especially in a case like that of coronavirus, which continuously mutates with new and varying symptoms that often overrules the effectiveness of COVID vaccinations.

Also Read: Mumbai doctor gets COVID thrice, twice after full vaccination

Owing to this and many such factors, experts often refrain from giving the process a hard timeline. Still, in this article, we will attempt to analyse the progress of India towards her immunity building.

What is Herd Immunity?

Herd immunity is when immunity in a population is high enough to block the pathway for the ongoing transmission of the disease. This immunisation comes either from the artificial injection of antibodies (vaccination) or natural development of antibodies (in case of people infected and recovered from the infection.)

Why is herd immunity important?

Herd immunity is an important phenomenon because it blocks the way for the virus to further transmit. This can be understood this way, while vaccination provides each of us with direct protection against COVID, with herd immunity, even people who are unvaccinated would benefit because of that blocked transmission pathway.

Also Read: COVID Delta variant most contagious, infects vaccinated people too: Experts

Here is why experts don’t give a timeline of herd immunity building

Variations in COVID vaccines

A single herd immunity figure is difficult to estimate when the infectiousness of SARS-CoV-2 (the virus that causes COVID-19) remains so variable. Experts analyse the infectiousness of a disease by looking at the R0, or reproduction number — the average number of people infected by one case where no control measures are in place.

The ancestral strains of SARS-CoV-2 have an R0 of 2-3, but Delta is estimated to be twice as infectious, with an R0 around 4-6.

The type of vaccine, doses given (whether one or both), and how well the vaccines cover the different variants all factor in.

Estimates from the United Kingdom show two doses of the Pfizer vaccine are between 85% and 95% effective against symptomatic disease with the Alpha variant, while two doses of AstraZeneca are 70% to 85% effective. Overall vaccine effectiveness appears to drop about ten percentage points with the Delta variant.

Disparity in global vaccination

While nations focus on to mass vaccinate their population and developed countries are constantly extending support to less privileged countries in every way possible, the process has several disparities and process loopholes.

Also Read: How Bhutan managed to vaccinate most of its population

Some nations take more time, some do not have vaccines, some vaccines are not effective against all the variants and many others is what leads to a difference in vaccination.

Untill, there’s more stability in the vaccine-related functioning at a global level, it is hard to say when we will reach herd immunity.