Coronavirus: Are Indians more immune to Covid-19?
Back in the early days of Covid spreading to Italy and other parts of Europe, there was talk about why Indians shouldn’t worry given our superior immune systems that has fought several diseases arising from the poor hygiene levels in the country. Such talk disappeared as the country rose through the ranks to become one of the worst affected at least in terms of absolute number of infections. Now that India has shown consistent decline in new cases over the past month and a half with significantly lower death rates than global average just when the developed world is seeing a second wave, there is a revival of that hypothesis. This piece in the BBC cites two papers which are yet to be peer reviewed, but postulate that the higher immunity may have caused the low fatality rates in India and other developing countries. The author in the end however cites experts who question the causation and instead ascribe other factors such as the younger demographics as a more plausible reason for the low death rates and the fact that there is still a lot more to be learnt and known about this virus itself.
“Millions of Indians have limited access to clean water, consume unhygienic food, breathe foul air and live in densely packed surroundings.
Researchers have found this makes them susceptible to a host of non-communicable illnesses like heart and chronic respiratory diseases, cancer and diabetes. These contribute significantly to the disease burden, according to a government report. Air pollution alone kills more than a million Indians every year.
…India has a sixth of the world’s population and a sixth of the reported cases. However, it accounts for only 10% of the world’s deaths from the virus, and its case fatality rate or CFR, which measures deaths among Covid-19 patients, is less than 2%, which is among the lowest in the world.
Now, new research by Indian scientists suggests that low hygiene, lack of clean drinking water, and unsanitary conditions may have actually saved many lives from severe Covid-19.
In other words, they propose that people living in low and low middle-income countries may have been able to stave off severe forms of the infection because of exposure to various pathogens from childhood, which give them sturdier immunity to Covid-19. Both papers, yet to be peer reviewed, looked at deaths per million of population to compare fatality rates.
One paper compared publicly available data for 106 countries on two dozen parameters like density of population, demography, prevalence of diseases, and quality of sanitation. The scientists found more people had died of Covid-19 in high income countries. “People in poorer, low income countries seem to have a higher immunological response to the disease compared to high income peers,” Dr Mande, one of the authors of the study, told me.
The other paper looked at the role played by microbiome – the trillions of microbes that reside inside a human body – in Covid-19 infections. Microbiome includes bacteria, viruses, fungi and single-celled archaea. They help in digestion, protect against disease-causing bacteria, regulate the immune system and produce vitamins.”
“Scientists say since correlation does not imply causation, such studies should be strictly regarded as observational. Also, as Dr Mande says, “this should not be inferred as our advocating a move towards weaker hygiene practices for handling future pandemics”.
Krutika Kuppalli, an assistant professor in infectious diseases at the Medical University of South Carolina, says the new research takes into account a variety of assumptions that have not been scientifically proven. “They are more hypothesis than scientific fact,” she says.
Also, epidemiologists have attributed the low fatality rate in countries like India to a young population – the elderly are typically more vulnerable. It is not clear whether other factors, such as immunity deriving from previous infections from other coronaviruses, are also responsible.
Clearly, a range and variety of reasons could be possibly behind the low fatality rate. “We still have a lot more to learn about the virus as we are still only 10 months into the pandemic,” says Prof Kuppalli. The fact is there is much we don’t know.”