High sero prevalence in cities indicate India’s IFR might be low, despite...

High sero prevalence in cities indicate India’s IFR might be low, despite doubts about under reporting of deaths


MUMBAI: Indian cities Mumbai, Pune and Delhi have the highest sero prevalence anywhere in the world, yet epidemiologists are divided on whether to declare whether these cities are closer to reaching “herd immunity” as there is still no clear indication on how long the infected people remain protected from the infection.

However, there is growing consensus that the infection fatality rate (IFR) might be much lesser for India, despite the doubts over the accuracy of Covid death numbers in India. Sero surveys are conducted to check to what extent a population has been infected and sero studies indicate the antibodies that populations develop in response to an infection.

On Monday, researchers from Pune’s Savitribai Phule University presented their findings of the sero study conducted in the five densely populated areas of Pune city and found that 52% of the population had antibodies against the virus. The Pune sero survey was in line with the trend seen in Mumbai that showed 57% of the people in the city’s slums had been infected with the disease.

In Delhi, the sero survey conducted on 20,000 households in 11 districts of the national capital found 27% had antibodies in high prevalence areas. These sero surveys are the highest in the world.

“I am not shying away from saying that this is reasonably good news if we had counted our beds and poor outcomes well enough. We may be actually getting to a reasonable level of population immunity. However this is not definitive and we still need to see whether these are neutralizing antibodies (protective from re infection) and if these antibodies are uniform across people,” said Jacob John, Professor of Community Health, CMC Vellore- who was advisor to the researchers of the Pune sero study. John says when researchers went into the study, they had expected the sero prevalence to be around 10-15%, but data indicate that the spread has been much higher. However, deaths corresponding to the cases is low.

“Without getting into the debate about how much mortality is correctly attributed to Covid, on the face of it, IFR is low and there could be several reasons for it, like pre-existing immunity from other coronaviruses, etc.”. John explained.

The other factor to look at while reading the results from these surveys is that perhaps we might see herd protection in a population happening at a threshold of 60%. There might be some kind of plateauing of infection that might start to happen. However, for public health officials to determine the falling number of cases, we also need to do extensive testing, professionals like John suggest.

“I do agree that for now, even when the people are infected to this extent, and the total number of deaths is not proportionately high, we can assume that the infection fatality rate is very low,” said Giridhara Babu, Head, Life course Epidemiology, Public Health Foundation of India (PHFI). Babu added that the focus now for India should be to prepare its tier 2 towns that will start seeing similar trends and might not be prepared to deal with rise in infection because of poor access to healthcare.

T Jacob John, India’s leading virologist & former professor CMC Vellore (different person than one quoted above) is of the view that though on the face of it the disease might not be severe, it affects different people in different ways and this has also exposed the deep rooted issues with our public health system.

“About the platitudes of low IFR, tell this to a person who has lost their family member to Covid-19. So fundamentally, we need to question our health care facilities, even though epidemiologically the disease is not as bad as people feared it to be,” T John said.

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