COVID-19: Herd immunity may be achieved at 43%, say experts

As COVID-19 cases surge across the country and vaccines and other treatment strategies are being devised, the state of affairs has thrown many in limbo. There is no one cure or prevention plan for coronavirus. Asymptomatic cases are on the rise, and most importantly, it is affecting everyone differently.

In the past, there were early doubts which said that the only option of "defeating" coronavirus would be to achieve herd immunity, which, by means signified that at least 70% of the population would have to be infected by the virus for them to "gain" immunity from it. Not only did this number seem risky, but there were also a lot of factors which negated the working of this concept. However, newer studies suggest that achieving herd immunity, for coronavirus might actually be possible, and that too at a low percentage rate of 43%.

Herd immunity happens when a large percentile of people across a community become naturally immune to a disease's spread and thereby, prevent the transmission from further happening. It can happen in two ways- either by injection of a vaccine which negates the working of the virus, or when a person actually gets infected.

Traditionally, statistics suggest that to achieve herd immunity, a community needs to achieve a 60% rate. However, a new study conducted jointly by University of Nottingham and University of Stockholm, results of which have been published in Science Journal found out that a region could actually achieve herd immunity and break the chain of transmission at a lower percentage, giving hope to the idea that achieving immunity against COVID-19 might be possible.

The countrywide study categorized people belonging to different age groups, based on their age, social activity and health.

The study devised six age categories and three activity categories: high, medium and low; and assumed that within each age bracket, 50% have normal activity, and 25% each have low and high activity level. The basic reproduction number, or the number of people infected by one patient, was assumed at 2.5.

Over weeks of time, it was observed that those who were more socially active were likely to get infected and more so, age did not have a factor to play in catching the infection.

One of the authors involved in the study wrote, "Our findings have potential consequences for the current Covid-19 pandemic and the release of lockdown and suggest that individual variation (in activity level) is an important feature to include in models that guide policy,"

"By taking this new mathematical approach to estimate the level for herd immunity to be achieved, we found it could potentially be reduced to 43 per cent and that this reduction is mainly due to activity level rather than age structure,"

It was also seen that those who were more socially active were likely to transmit the disease onto others, as compared to those who stayed confined indoors or had lesser whereabouts.

There are both pros and cons of herd immunity, but there is no conclusive proof that it works to eradicate the pandemic. While herd immunity does provide a community respite from the viral infection, one of the biggest risks is the loss of human lives, which is something no country can afford.

Secondly, there is no real surety or scientific proof that those infected by coronavirus won't get infected again. Even though patients gain antibodies to recover faster, we do not have conclusive evidence of how long the immunity lasts. Same happens with a vaccine injection. Preliminary reports suggest that even with a vaccine dosage, we might only gain immunity for upto a year, implying that instead of eradicating the infection, we might have to learn to live with the virus.