Are Indians more immune to Covid-19? | Hacker News Reader

Are Indians more immune to Covid-19?

bbc.com

The paper in question: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7444648/pdf/mai...

It is indeed very interesting and worthy of consideration that Indians and other people from poor countries with lesser hygiene may be more immune to COVID infections.

India's government lifted its infamous lockdowns at times when the number of active cases only seemed to be flying upwards and had no anticipations of coming down anytime soon. In a poor, extremely overpopulated country with high rates of overcrowding and very low hygiene standards, coupled with rampant unemployment and economic distress, anyone could have only expected the situation to worsen. And it did - the country's GDP shrunk by almost a quarter and cases continued to pile up... until they didn't. The number of active cases miraculously peaked mid-November and have been in a healthy downward trend since. While developed countries like the UK seem to have their number of active cases shoot up exponentially, many states in India are experiencing a net decrease in cases to very safe levels. Even infamously overcrowded states like Uttar Pradesh are displaying impressive levels of recovery.

One has to reckon there must be something more to it than just government interventions and change in attitudes.

> peaked mid-November

Typo? We're not mid-November yet.

They did have a peak in mid September, perhaps that was the intended word.

yes. Apologies.

I'm always skeptical of these studies because I suspect there's more documentation and reporting biases in more socioeconomically stressed areas. That is, my guess is cases are less likely to be accurately documented in India than, say, the US or Germany.

Having said that, there's molecular biological evidence of cross immunity to other forms of coronavirus so there might very well be something to it.

I've wondered along these lines if keeping kids out of schools might in some ways be counter productive, by decreasing exposure to other coronaviruses or other pathogens that increase immunity.

I've often wanted to see if, eg, parents of young children, or people working with young children (teachers, pediatricians, etc) have less severe outcomes from sars-cov-2 than matched controls.

Edit: mid-September, not mid-November.

No country has experienced exponential growth. Exponential growth is unbounded and impossible with a finite population. The number of total infections is better described by a logistic function (epidemiologists use more sophisticated models of course, but the shape of the curve is similar).

About 28% of the Indian population has been infected (15-22% according to more pessimistic estimates). In some areas it's even higher, 41% in the slums of Mumbai.[1] The virus is running out of hosts. That is not a miracle, it's completely expected.

[1] https://www.sciencemag.org/news/2020/10/indias-covid-19-case...

The headline doesn't match the content. The content proposes not that they are immune, but that the rate of death, after getting COVID-19, is lower than the rest of the world. The rate of cases for India is similar to everyone else.

Have they accounted for the age? The indian population is younger than the west on average.

Yeah, I'm just not sure what's happening in Asia, South America, and Africa. There were stories about lots of cases in a few countries but the number of deaths was quite low. Europe and North America seem to be the brutally hit but other places seem to have got through the pandemic without much trouble.

Is it the vitamin D? We should really try to figure out why these regions have done so well and try to replicate that in Europe and NA.

> I'm just not sure what's happening in Asia, South America, and Africa.

Latin America seems to be all over the list of top deaths/capita for the whole pandemic, but currently the worst places (per capita deaths in the last 7 days) seems to be mostly central/eastern europe, though Argentina is pretty high in both all time and recent deaths/capita.

Where Africa is doing well or just doesn't have good surveillance to even identify cases, I couldn't say. But if a place doesn't have much inbound tourism, doesn't have lots of people able to afford international travel, and doesn't have the kind of internal mobility common in the developed world, it would make sense that they might not get hit very hard without taking much in the way of special precautions.

The inbound tourism idea is something I didn't think about. Transmission may depend a lot of people transporting it from one geographical region to another, and that might be less common in the developing world simply due to worse transport networks and people living and working more locally in general. E.g., more people from the UK go to Spain on holiday than people from Gambia.

In all those countries they extensively use Hydroxychloroquine which is anti malaria drug and super important especially in Africa. Indian government is very open in using it for covid-19: https://www.newsweek.com/india-promotes-hydroxychloroquine-d... As well as many African countries: https://www.voanews.com/covid-19-pandemic/djibouti-treating-... https://www.theafricareport.com/26726/coronavirus-recovery-r...

can provide more sources if requested (or just google it)...

Given how central Vit D seems to be sun exposure seems like a relevant factor too. Much of Africa for example seems to be coping pretty well

Will training the immune system against allergens help fight real pathogens better? Can childhood exposure to pets, camping, gardening or even supplement pill full of allergens boost total immune system function?

It depends on how similar the 'antigens' on the allergens are to antigens on SARS-CoV-2. They're probably not super similar, so they wouldn't help the immune system fight better. Instead, it might do something equally valuable in teaching the immune system to chill-out via increased diversity of Treg cells. It's a big deal in kids because they still have a thymus, and they're training a TON of Tcells.

https://www.immunology.org/public-information/bitesized-immu....

"As the name suggests regulatory T cells (also called Tregs) are T cells which have a role in regulating or suppressing other cells in the immune system. Tregs control the immune response to self and foreign particles (antigens) and help prevent autoimmune disease. Tregs produced by a normal thymus are termed ‘natural’. Treg formed by differentiation of naïve T cells outside the thymus, i.e. the periphery, or in cell culture are called ‘adaptive’."

In this case, it might be a matter of exposing the immune system to more pathogens so that it doesn't freak out when it sees them:

"In medicine, the hygiene hypothesis states that early childhood exposure to particular microorganisms (such as the gut flora and helminth parasites) protects against allergic diseases by contributing to the development of the immune system. In particular, a lack of exposure is thought to lead to defects in the establishment of immune tolerance. The time period for exposure begins in utero and ends at school age."

https://en.wikipedia.org/wiki/Hygiene_hypothesis

The immune system self-regulates. Otherwise it would constantly be freaking about about every food you eat or every particle in the air you breathe in or whatever. One of the primary issue with coronavirus is the cytokine storm resulting from the immune system freaking out, and one of the most effective front-line treatments is steroids to knock-down the immune system. So, by letting kids sneeze on each other and play in the mud and catch all the colds and stuff, you're allowing their immune system to develop 'tolerance' to benign stuff in the environment. There may be something like that at play here.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7365923/ Tang Y, Liu J, Zhang D, Xu Z, Ji J, Wen C. Cytokine Storm in COVID-19: The Current Evidence and Treatment Strategies. Front Immunol. 2020;11:1708. Published 2020 Jul 10. doi:10.3389/fimmu.2020.01708

"They define that “cytokine storm” is an activation cascade of auto-amplifying cytokine production due to unregulated host immune response to different triggers. The triggers involved infections, malignancy, rheumatic disorders, etc."

Yeah, so cytokines are just immune system signaling molecules. For some reason, Coronavirus causes the immune system to completely lose it's shit in some people. So, it's theoretically plausible that the more coronaviruses (common colds) you were exposed to as a kid, the less your immune system will overreact because it's seen something similar before many times.

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