Can New Mortality Data Explain India's Low COVID Death Numbers?
As researchers caution against declaring India's second COVID-19 wave to be less deadly than the first, we look for clues in excess mortality data from Kerala and Mumbai to shed light on India's comparatively low COVID-19 mortality
Chennai: More than one year into the COVID-19 pandemic, India is beginning to take the first steps towards answering a key question--is there something unusual about COVID-19 mortality in India? Mortality is at the heart of the question of whether India has been an outlier in the global trajectory of the virus, or not. Despite having the third-most confirmed COVID-19 cases globally, behind only the US and Brazil, the US has 3.5 times as many deaths as India, and Brazil is moving closer to double India's deaths.
India's position as an outlier on COVID-19 fatalities rests on the assumption that India is accurately counting COVID-19 deaths. To varying degrees, all countries are undercounting COVID-19 deaths because, for instance, deaths due to the disease could be attributed to other causes in cases where COVID-19 was not diagnosed.
Enter: all-cause mortality data.
Many cities and countries are now estimating the number of COVID-19 deaths they missed by comparing current estimates for deaths from all causes with previous years'.
South Africa, for instance, estimated "the actual number of deaths that have occurred in the country and calculate[d] the number of excess deaths over and above the numbers that would be expected had the historical mortality trends prior to the COVID-19 pandemic continued". In doing so, South Africa found that the cumulative number of excess deaths from natural causes between May 3, 2020 (after the country's first COVID-19 lockdown) and January 23, 2021 (during the country's second surge of COVID-19 infections and second lockdown) was greater by 125,000 than the numbers predicted by historical trends.
Is India also missing counting a substantial number of deaths that could potentially be attributed to COVID-19? It's possible, given that over two out of every three registered deaths in India occur at home, and just 86% of all deaths are registered, meaning that 14 of every 100 deaths in India go entirely uncounted. It has also been near-impossible to answer this question since the beginning of the pandemic, since India's Civil Registration System (CRS) data are released only after a considerable time lag; data for 2018 were released in June 2020.
While India's CRS data for 2020 are awaited, others have assembled data from novel sources. Renuka Sane, associate professor at the National Institute of Public Finance and Policy (NIPFP), and veteran economist Ajay Shah analysed the Centre for Monitoring Indian Economy's (CMIE) Consumer Pyramids Household Survey (CPHS) data on deaths for a pre-print paper. The CPHS is a panel of 232,000 households, meaning that the surveyors meet the same households thrice a year. While CPHS data are typically used for economic analyses, the survey also incorporates a wealth of data on socio-economic indicators including health.
Sane and Shah studied CPHS data on the whereabouts of each family member, and found that deaths from all causes between May and August 2020 numbered almost twice as many as compared with the same period in past years, they told IndiaSpend. While the survey does not ask about the cause of death, Sane and Shah argue that COVID-19 alone might not explain away the increase, particularly among poorer households, rural households, women and the non-elderly. Socio-economic factors triggered by COVID-19 or disruptions in health services could have played a role, but the CPHS data do not provide clues to the cause, they said.
Kerala records fewer deaths overall during the pandemic
Some Indian cities and states have released all-cause mortality data, which paint a complex picture. Kerala released its state-wide all-cause mortality data in February, which showed that the state, despite accounting for the second highest number of COVID-19 infections in India, recorded over 16,000 fewer deaths in 2020 compared to the average of the previous five years.
Kerala's health department was quick to declare that "[t]his is the result of all preventive and promotive steps taken by the Government of Kerala during 2020". Experts in the administration, however, are more circumspect.
"At the beginning of the pandemic we hypothesised that if we reduced deaths from COVID-19 with good case management, the lockdown could lower all-cause mortality on account of factors including a reduction in road accidents, lowered respiratory infections due to masking and social distancing, fewer gastrointestinal infections on account of better hand hygiene, and absence of medical errors in a population known to over-consume healthcare. If this happened, the number of deaths from COVID-19 would be offset by this reduced mortality from other causes," Rajeev Sadanandan, the state's former health secretary and current COVID-19 adviser to the chief minister, told IndiaSpend.
"But soon, we realised that death registration, which used to be near 100% in Kerala, had come down due reduced mobility, reluctance to visit government offices, increase in the number of home deaths due to reluctance to visit hospitals, etc.," Sadanandan said, "So while the data does seem to be showing reduced all-cause mortality, it's too soon to come to any conclusion. Only after the death registration data is updated, or the variance between actual and registered death is calculated, can we say definitely whether mortality has come down during the pandemic period. We also need to see whether delayed treatment and the medium-term consequences of COVID-19 will increase mortality in the immediate future."
Mumbai sees 22% more deaths in 2020
The second region in India to have released all-cause mortality is Mumbai, and here the city shows a substantial increase in deaths between each of the previous five years and 2020. This is despite the fact that accidental deaths--significant in a city where an average of seven people died every day on train tracks in 2019--would have dropped substantially during the lockdown.
How many of the 21,000 excess deaths in 2020 were on account of undiagnosed COVID-19 will be hard to ascertain; Mangala Gomare, the city municipal corporation's executive health officer, reportedly said that the causes of death were still being ascertained. But given the city administration's refusal to classify any deaths among people who did not test positive for COVID-19 prior to death as being from COVID-19, the city is unlikely to accept that these were undiagnosed COVID-19 deaths, a city health official told IndiaSpend, requesting anonymity. Additionally, the city's hospitals saw substantial COVID-19 as well as non-COVID-19 referrals from nearby districts in 2020, Oommen C. Kurian, senior fellow and head of the health initiative at the Observer Research Foundation, a think-tank, pointed out.
Prabhat Jha is the world's foremost expert on mortality in India, and is founding director of the Centre for Global Health Research in Toronto and professor of disease control at the University of Toronto. Jha led the Million Death Study in collaboration with the Registrar General of India that produced verbal autopsy-led cause-of-death estimates from 2001 to 2013 in India.
"The Kerala reports are based on civil registration, which can miss deaths. In particular there are reports that the proportion of home deaths rose in Kerala in the last year, so this might be part of the explanation," said Jha, who has been advocating for India to conduct a rapid household sample survey to ascertain the level and causes of mortality in 2020. "The reported 10% drop in overall mortality in 2020 from 2019 in Kerala needs to be confirmed by the Sample Registration System."
"If [drop in overall mortality] is true, the 10% lower deaths at all ages is not due to lower accidents, as these are only 10% of all deaths. And if true, this would be important to understand what's going on as Kerala with its older age distribution than India could have had more COVID-19 deaths than observed," Jha said, adding, "Overall, Kerala does have a better public health system and the more widespread testing and contact tracing and isolation may have played a role in keeping deaths low."
In Mumbai, on the other hand, the increase in adult deaths is most likely on account of undiagnosed COVID-19, Jha said. "The absolute number of extra adult deaths is about 25,000, while for Maharashtra overall, the cumulative COVID deaths by January 1, 2021, were about 50,000. I suspect then that the excess deaths in Mumbai were mostly [from] COVID, with no clear offsetting increases or decreases in other causes. But this would need detailed data to be released," he said.
All of this once again becomes important as the second wave of COVID-19 infections gathers steam in India. While cities like Mumbai and Pune have returned to daily new cases comparable to or surpassing their first peaks, daily reported deaths are still some distance behind. So does this mean that the second wave is resulting in fewer deaths?
It's too soon to declare that the second wave is less deadly, particularly since cases are growing far faster than the first time around, said Murad Banaji, lecturer of mathematics at Middlesex University, UK, who has been closely tracking India's COVID-19 numbers. Deaths can take some time after cases start rising to show up for several reasons, he told IndiaSpend. For one, when active infection is low, a statistically large enough pool of infected people needs to develop for deaths to start occurring. Then, deaths usually take weeks after the confirmation of a case to show up in the data. Finally, cases might first occur among less vulnerable groups like young people, and take some time to spread to the elderly where deaths are more likely to occur, he said. "It would be incredibly premature to declare based on the current data that mortality is lower in this wave," Banaji said.
It still does appear that at least in parts of India, mortality from COVID-19 has been substantially lower than in the rest of the world. "The few cities in India which have reported on overall deaths by week regardless of cause do show a big increase in overall deaths when COVID-19 deaths rose, suggesting that much of the increase in overall deaths are likely to have been COVID-19," Jha said.
The degree of under-reporting of COVID deaths varies, but Jha believes that it is in the range of 10-20% in big cities like Mumbai and Delhi, and not say 100% or so. Based on this presumption, India could have more deaths from COVID-19 than its official count, but relatively low undercounting would not dramatically alter the Indian picture.
Further, India has reported substantially lower Infection Fatality Rates--deaths relative to total infections--than many other countries; the last official estimate put India's IFR at under 0.1%, while the United States Centre for Disease Control pegs the US IFR at 0.65%. But in rural India, the truth is that we simply don't know what is happening with COVID-19 infection and deaths, he said.
If fatality rates truly have been lower in India, what could explain it? Observations from Vietnam and Thailand suggest some cross-immunity, perhaps from other circulating bat coronaviruses in the region, said Jha, and this is worth studying in India. Another possible explanation for India is widespread low-grade COVID-19 infection, he said.
"My sense is that we'll know the real toll of the pandemic (and the potential impact on other causes of death) only years from now, when the patient work of counting the dead and describing causes is more complete," Jha said, "Better antibody studies in the whole of India would help. Till then, we've got to try to use the limited data to track the epidemic."
And for now, COVID-19 vaccination must ramp up, Kurian and Jha both say.
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Correction: The story has been updated to correct the units in chart 4.