The survey’s new estimates produce Covid-19 mortality rates for India that are lower than virtually anywhere else in the world in order of magnitude, but the narrative around these mortality rates can undermine India’s understanding of the disease by being too fast to characterize them. to the government’s “successful strategies” rather than looking for the underlying biological and sociological reasons that could do them, experts say.
The Indian government reiterates that India’s mortality in Covid-19 is low compared to the rest of the world, and Prime Minister Narendra Modi also praised this indicator, which is mainly based on a crude measure called the casuistic rate. as recently used, it is only the total number of Covid-19 deaths reported on a given date divided by the number of Covid-19 instances shown on that date.
But a CFR number for singles for a country does not take into account a number of points that that number – the maximum important, the age. All the evidence to date has shown that SARS-CoV-2 is disproportionately for the elderly. a relatively young country, this may decrease its CFR, experts have suggested.
However, several studies have shown that, given age, age-adjusted Indian CFR is low.
In a recent discussion paper through the National Bureau of Economic Research, for example, economists Minu Philip and Debraj Ray and researcher S Subramanian find that the age-adjusted mortality rate of Covid-19 in India is higher than would be expected if the case of age-specific fatality rates in 14 countries , adding some European countries that evolved from East Asia and Latin America, have been implemented in India. While India is particularly younger than these countries, its young population has also been disproportionately affected, according to its article.
“Among adult teams and compared to comparison countries, India has a higher rate effect for everyone, but also for the elderly. These relatively young and middle-aged teams are not only the most represented in the general population, they are also disproportionately most affected by Covid-19,” they write.
As the pandemic progresses, many members of the public and clinical physical fitness network are moving away from calculating CFRs based solely on recorded instances of Covid-19 mortality in the general population; India is once again emerging as an outlier (read our past stories on undercounting Covid-19 instances and deaths here, here, and here).
Worldwide, serological surveys consistent with researchers estimate the scope of SARS-CoV-2 antibodies in the population and therefore the infection mortality rate. numerator as in the CFR, but divided by the estimated total number of infections in the population, whether or not they have already been detected (researchers would use the extent of the spread of infection shown by serological surveys to estimate the total number of cases detected and not detected in the population. )
In early July, the World Health Organization’s leading scientist, Soumya Swaminathan, this IFR derived from the world somewhere in the 0. 6% range.
Other global studies have found the same; the US Center for Disease Control “current estimate” (as of July 10) for the IFR is 0. 65%. A meta-analysis of global estimates in early July estimated the IFR at 0. 68%.
And then there are the Indian estimates.
Since the beginning of July, seroprevalence surveys have been conducted across the country. In June, the Medical Research Council of India presented for the first time the first effects of a pan-Indian serological survey that divided the country into 4 teams from 15 districts, ranging from a low occurrence of what rt-PCR control showed at the time, with a maximum occurrence. This survey revealed a seroprevalence of 0. 73% and an IFR derived from 0. 08%.
The National Center for Disease Control conducted a stratified serological survey in Delhi from 27 June to 1 July, which they said showed 23% seroprevalence and an IFR derived from approximately 0. 07%. The moment cycle through Maulana Azad Medical College in The week of August revealed that seroprevalence was greater than 28%, resulting in an IFR derived from approximately the same value.
In Mumbai, the Tata Institute for Fundamental Research, Niti Aayog and the Greater Mumbai Municipal Corporation collaborated on a serological survey conducted in 3 districts of the city, each of which is a neighborhood of low, moderate and high prevalence, discovered in what exists RT-PCR tests showed the pattern stratified by age and gender, and divided into slums and not slums. Researchers found that the prevalence of 51-58% in the slums of the 3 wards and 11-17% in spaces other than slums This produced an IFR derived from 0. 05% to 1%.
A serological survey in Pune revealed even higher seroprevalence, which would mean an even lower derived IFR.
The degrees of seroprevalence demonstrated through serological surveys in Delhi, Mumbai and Pune would mean IFR of an order of magnitude decreasing than overall estimates. “Even if there is a significant underestimation of Covid-19-related deaths in India, this will materially mean adjusting those rates,” said Giridhar Babu, epidemiologist at the Indian Public Health Foundation, in an interview with IndiaSpend. The explanation for why India produces such weak IFRs is something that requires further investigation, he said. But even before that, the agencies that conducted the Indian polls rushed to characterize the abnormally low IFR from the “successful” measures taken by governments.
Presenting the initial effects of the first ICMR national serosurvey on June 11, Balram Bhargava, ICMR Director General, attributed the low seroprevalence (less than 1% at the time) to the government lockdown, saying: “The The news is that the death rate from infections is very low.
At the same press conference, VKPaul, who heads the Covid-19 reaction working group, said: “In such a giant country, such a giant pandemic has remained at this point across the country, this in itself is a very vital achievement. , there is no doubt about it. ‘ He added: “The mortality rate in this country from the pandemic is obviously low. And it’s also a matter of luck. “
In July, HIV prevalence is no longer low, but IFRArray and government policies were praiseworthy.
“This shows us one more thing that competitive blockage measures or containment measures taken from the outset prevented this infection from taking a serious form. This shows the good luck of these measures,” said the director of the National Center for Disease Control. Sujeet Kumar Singh, presenting the effects of his Delhi survey, which they said showed showed that 23% of the population had antibodies.
In a technical note accompanying the Mumbai survey published through TIFR, the authors say that the city’s low IFR can simply be attributed to “effective containment efforts and active measures to isolate symptomatic instances through MCGM”. Later, they recommend that “social estating and similar precautions, such as dressing in a mask, are effective in delaying the spread of infection. “
These claims do not answer a key question: if infections appear to have spread more widely in India than almost anywhere in the world to produce HIV levels in some other countries, what happens in India that helps keep deaths so low?The only explanatory variable was “successful containment measures,” do you deserve South Korea to do better?
The low-referral IFR is not the result of an overestimation of seroprevalence, but it may have several other explanations, Singh, the ncDC director, told IndiaSpend. “We have a very young population, so it may just be an explanation Then another explanation is that our population might have underlying immunity,” he said. However, age, as a complete explanation of India’s ” low mortality, is controversial, given India’s unusually high age-adjusted mortality for younger age groups.
TIFR’s leading researchers for the study, scientists Ullas Kolthur-Seetharaman and Sandeep Juneja, gave explanations in an interview with IndiaSpend.
First, the age-adjusted IFR is not of an order of declining magnitude in India, Juneja said: “If you had to adjust according to age, the IFR for Spain or even Wuhan would be about 0. 2% and what we see is 0. 1%. ” He said. The underlying immunity, he said, may only partly be this deficiency. “The IFR in our survey is really lower for slums and higher for non-slums. If you look at spaces other than slums, it’s really very similar to who you are. waiting — it’s actually more than 0. 2%. You can speculate on the reasons for this scenario – the population of slums may be younger, slum dwellers may have weaker comobility and, thirdly, may have developed some immunity,” he said.
Although none of these explanations were found to have a proven link to decrease mortality, they may only provide guidance for studies.
Today, there is an emerging way of thinking about how this immunity can be studied. Priya Sampathkumar, President of Infection Control at mayo Clinic in Rochester, Minnesota, USA. The U. S. , recently created a Twitter channel of emerging global evidence on immunity cross-reaction, as indicated through the presence of reactive T cells to Covid-19 (immune reaction cells) that provide others without exposure to the virus.
“I think that may just be the drop in mortality [in India],” he said in an interview with IndiaSpend. ‘Even if a lot of other people are infected, the disease is more benign due to pre-existing cross-immunity from an infection beyond other coronaviruses.
Continuing this speculation would require testing the immunity of T cells, which Sampathkumar says is much harder to measure than antibodies. In addition, the presence of cells does not guarantee that they produce effective immunity in a person, and in India, there is a specific concern: “Nutrition has a significant effect on T-cell immunity”.
It has still been established whether India’s low IFR point is a biological fact or the product of its younger population; Murad Banaji, senior professor of mathematics at Middlesex University in London, analyzed age-adjusted IFRs and found that age-adjusted IFR in Mumbai is inexplicably the best in the 40- to 60-year-old age group.
What is clear, however, is that a general compliment to the government for “keeping” the IFR at a low point will not take India’s understanding of the pandemic very far. “People are taking those low IFR values very temporarily to the letter that from serological surveys without actually looking to unpack them and wonder why,” Banaji said.
In the absence of transparent evidence that there is something materially different in India, much remains to be done to explain why this is happening, Babu said.
Rukmini S is a freelance journalist in Chennai.
This copy was published as part of a special agreement with IndiaSpend.