The Elusive Herd

The Elusive Herd

September 11, 2021 0 By Joe C Mathew

India cannot bank on herd immunity to protect its population from Covid-19

Joe C Mathew

On February 2, Satyender Jain, minister of health, Delhi, tweeted that the national capital has largely won over Covid-19. The results of the fifth sero survey done in the state had just come, and antibodies had been detected in 56.13 percent of Delhi’s population, triggering the tweet. The minister was suggesting the possibility of ‘herd immunity’ – defined by World Health Organisation as an indirect protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection – against Covid-19 among Delhi residents. 

Jain couldn’t have been more wrong as the Delhi government had to interrupt its sixth round of sero survey a couple of months later due to a surge in Covid-19 cases and subsequent lockdown. The results of the sixth round also found approximately the same percentage of population carrying antibodies of the Covid-19 causing SARS COV-2 virus, though there were no tall claims made this time. The Delhi minister was not the only person to express such short lived optimism. The National Institute of Disaster Management, in its latest report on “Covid-19 Third Wave Preparedness”, says that earlier, “it was proposed that if 67 percent of the population became immune (a few by infection and rest through vaccination), herd immunity could be achieved”. It adds that due to the appearance of new and more virulent mutated variants of SARS Cov-2, the target immune population level (sero-prevalence) for achieving herd immunity is now 80-90 percent. “Our health system and vaccines are caught in a race against the virus and are trying to catch up with risks that are evolving every day, creating uncertainty all over the world”, the report said.

Is 80-90 percent immunity good enough? 

Even that seems to be unrealistic. In fact, countries like the US, UK and Israel where Covid-19 vaccinations have covered 50 percent or more of the population (Only about 10 percent of Indians have received two doses of Covid-19 vaccines so far) are all witnessing a resurgence of  Covid-19 infections now. Therefore, India’s hopes of arresting the spread of the pandemic through herd immunity seems misplaced. Public health experts, virologists and medical practitioners that Future Medicine spoke to are near

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