Covid-19 Partial existing immunity in unexposed populations

In summary, a recent study has found that unexposed humans may have selective and cross-reactive T cell epitopes for SARS-CoV-2, the virus that causes COVID-19. This is due to previous infections from other coronaviruses that cause common colds. It is estimated that 20-50% of the human population may have partial immunity to COVID-19 as a result. This could explain the high number of asymptomatic cases and could potentially lead to a universal vaccine. However, it is unclear if this immunity persists over time. It is also worth noting that this study does not include the enteric coronavirus group, which has caused outbreaks on cruise ships in the past. Further research is needed to fully understand
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jim mcnamara
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TL;DR Summary
A hypothesis to help explain the wildly varying responses to Covid-19
Selective and cross-reactive SARS-CoV-2 T cell epitopes in unexposed humans
Science 04 Aug 2020:
eabd3871
DOI: 10.1126/science.abd3871
URL: https://science.sciencemag.org/content/early/2020/08/04/science.abd3871

[Background]
The Coronavirus family of viruses is a cause of multiple human illnesses: diarrhea & vomiting (enteric), colds, SARS, MERS, Covid-19

Example from 2009, case reports on nasal mucosa damage from Coronavirus cold infections:
https://www.tandfonline.com/doi/abs/10.3109/00016488909127507

To reduce confusion, enteric Coronavirus infections - the ones that caused violent vomiting and diarrhea on cruise vessels a few years back - have been known since the 1970's example:
https://link.springer.com/content/pdf/10.1007/BF01314383.pdf
The enteric ones are NOT what the current paper is discussing.

Bottom line:
This means the previous exposure window to one of the Coronavirus cold agents in the paper under discussion is long. Whether or not partial immunity persists from way back then -- I did not find a reference that quantifies any of this.

It would be very interesting to see if immunity to Covid-19 could arise from some of the nasties cousins, and the possibility of a universal vaccine:
https://www.sciencedirect.com/science/article/pii/S0092867420308126

[/Background]


Paper discussion:
Populations of humans that have not been exposed to Covid-19 show some immune memory cells that can respond to the Covid-19 virus. This is due to previous cold causing Coronavirus infections. The authors estimate 20% - 50% of the human population has this partial immunity.Coronavirus colds have been known since at least the early 1980's - from 1986:
https://academic.oup.com/jid/article/154/3/443/819151

It does not appear to mention the enteric Coronavirus group, which should be of interest.

This would explain, in part, why so many people in modern populations exposed to the virus do not show severe symptoms - so-called asymptomatic infections. Because. The colds someone had a few years ago imparted partial immunity to the new virus. Not all colds are caused by this group of pathogens. Rhinovirus (another group of virus) also cause colds, for example.

Also remember that the cruise ship epidemics are caused by another enteric group of the virus family. It may be of value to explore this as another source of "stealth" Covid-19 immunity.
 
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Interesting. Reminds me smallpox and cow pox. I'd gladly take the 'cow pox' Coronavirus infection to avoid Covid-19.
 

Related to Covid-19 Partial existing immunity in unexposed populations

1. What is partial existing immunity in unexposed populations?

Partial existing immunity refers to the presence of some level of protection against a specific disease in a population that has not been previously exposed to the pathogen causing that disease. In the case of Covid-19, this could mean that some individuals may have some level of immunity to the virus even if they have not been infected before.

2. How do people develop partial existing immunity to Covid-19?

Partial existing immunity to Covid-19 can develop through various mechanisms, such as previous exposure to other coronaviruses (such as the common cold), cross-reactivity with other pathogens, or through genetic factors. However, the exact mechanisms and levels of protection are still being studied and are not fully understood.

3. Can partial existing immunity protect against severe illness from Covid-19?

There is some evidence that partial existing immunity may provide some level of protection against severe illness from Covid-19. However, the level of protection and the specific populations that may benefit from this partial immunity are still being studied and are not yet fully understood.

4. Is partial existing immunity a substitute for a Covid-19 vaccine?

No, partial existing immunity should not be seen as a substitute for a Covid-19 vaccine. Vaccines are specifically designed to provide targeted and controlled immunity against a particular pathogen, whereas partial existing immunity may not provide complete protection and may vary among individuals.

5. How does the concept of partial existing immunity impact public health measures for Covid-19?

The concept of partial existing immunity may have implications for public health measures, such as vaccine distribution and prioritization. It may also influence the effectiveness of herd immunity strategies. However, more research is needed to fully understand the role of partial existing immunity in the context of Covid-19 and its impact on public health measures.

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