Herd immunity has tamed Covid: Docs

Lucknow: The negligible Covid-19 cases in Lucknow over the past 100 days indicate that herd immunity is developing in the population against novel coronavirus due to high exposure during the second wave. This is the view of experts after analysing the transmission rate in the city since July.

Herd immunity develops in a population when 80% of the people are exposed to a virus. The ICMR serological survey has found antibodies against Covid in 71% of UP’s population, which indicates that a large section was exposed to coronavirus in the second wave, say experts.

This, experts predicted, has reduced the possibility of a third wave, and in case it comes, the intensity would be lower in comparison to earlier two spikes. However, if there is a mutation in the virus, a third wave could be devastating.

In such a scenario, people should not let their guard down and get vaccinated at the earliest, which will play a supportive role in maintaining herd immunity for long, eventually reducing the pandemic to an endemic, add experts.

“The development of herd immunity explains why cases have remained so low for such a long period. Lucknow has also done well on the vaccination front, which has made things more favourable,” said Prof Amita Jain, head of microbiology at KGMU.

“Research has concluded that herd immunity against Covid-19 develops when 80% of the population of a region has antibodies against it,” said Dr Rahul Gam, consultant at National Health Authority.

“The ICMR serological survey done in July found presence of antibodies in 71% of UP’s population,” he added.

“The few cases at present indicate that the virus is circulating but is not finding an adequate host to multiply itself because antibodies—formed either due to natural infection or vaccination—are neutralising it within the 4-5 days of incubation period,” said Dr Gam.

“As a result, people with antibodies are not falling ill or getting infected even after coming in contact with the virus. Besides, since the immune system is not allowing the virus to multiply, people are not passing it to others,” he said.

However, this does not mean that the threat is gone.

“The virus after entering a vaccinated person can mutate to evade antibodies. A person infected with the mutated variant can spread it to others. This variant becomes stronger with further circulation in the population,” warned Prof AK Gulati, ex-director of microbiology department at BHU-Institute of Medical Sciences.

“If the current transmission continues, there would be no third wave or a very weak one, but in case there is a mutation, the new variant can play havoc,” he added.

Experts also pointed out how the delta variant caused a surge in the US, UK and other European countries despite having a better vaccination record.

Epidemiologist Dr Amit Singh said the only way to prevent mutation is to strictly adhere to Covid protocols.