Could Pre-existing Immunities the Explanation of Taiwan's Mystery

Figure 1.  Number of new infections (08/17/2021; Source: Nikkei Asia)

Taiwan has seen extremely low cases and – more importantly – low death rates in the current COVID-19 pandemic.  On 11/07/2020, there is an article titled:^[1]

The Mystery Of Taiwan

published on the ZeroHedge website.  Here is the question asked in that article:

We are still left with a mystery. Taiwan did not lock down. It did not widely test. And yet it had the lowest death rate per million of any populous country in the world. It experienced 0.3 deaths per million and ranks 189th in the world.

As much as public health authorities in the West want to consider policy as a decisive factor in the success or failure of pandemic response, the Taiwanese case might have nothing at all to do with the public policy response.  

If public policy response is not the real explanation, then what is it?  Could it be pre-existing immunities?

Figure 2. Taipei 101 (right)

Pre-existing Immunity

An article published on Nature, it states that pre-existing immunity to common-cold coronaviruses or to other antigens could be another possible determinant of COVID-19 disease severity.  Here are the summary of the evidences presented in that article:^[2]

• T cell reactivity to SARS-CoV-2 has been detected in unexposed individuals.
• Presumably due to cross-reactive immunity to common-cold coronaviruses^[3] or to other antigens, as has been shown for other virus-specific T cells.^[4]
• A study found SARS-CoV-1 reactive T cells in patients who were infected with SARS 17 years ago.^[5]
• T cell reactivity is found in unexposed individuals and has been linked to prior exposures to common-cold coronaviruses.^[6]
•  IgG that is specific to SARS-CoV-2 spike protein has been found in unexposed individuals
• Particularly in children and young adults, and some of these had neutralizing activity against SARS-CoV-2, indicating a potentially protective effect against severe COVID-19.^[7]  
• However, another study also identified such antibodies but found no evidence for a protective effect against COVID-19.^[8] 
• Cross-reactive antibodies are also more frequently found in serum samples collected in sub-Saharan Africa prior to the COVID-19 pandemic.^[9] 
• This provides a possible explanation for the surprisingly low number of severe COVID-19 cases seen on this continent.

Conclusion

The real explanation of Taiwan's mystery could deal with innate immunities from other vaccines or virus exposures.  

Even though about 680 people in Taiwan were infected with SARS in 2003, the study shows a possibility that enduring T cells could influence the effect SARS-CoV-2 has on people with certain preexisting immunities. A different study found that there were strong differences in mortalities between Asia, the Middle East, Latin America, and Western countries, suggesting that genetic factors may also play a role in these disparities.

But, the above conclusion is just speculation without further proofs and scientific researches.

 

References

1. The Mystery Of Taiwan
2. Immune determinants of COVID-19 disease presentation and severity
3. Grifoni, A. et al. Targets of T cell responses to SARS-CoV-2 coronavirus in humans with COVID-19 disease and unexposed individuals. Cell 181, 1489–1501 (2020).
4. Su, L. F., Kidd, B. A., Han, A., Kotzin, J. J. & Davis, M. M. Virus-specific CD4+ memory-phenotype T cells are abundant in unexposed adults. Immunity 38, 373–83 (2013)
5. SARS-CoV-2-specific T cell immunity in cases of COVID-19 and SARS, and uninfected controls
6. Mateus, J. et al. Selective and cross-reactive SARS-CoV-2 T cell epitopes in unexposed humans. Science 370, 89–94 (2020).
7. Ng, K. W. et al. Preexisting and de novo humoral immunity to SARS-CoV-2 in humans. Science 370, eabe1107 (2020).
8. Anderson, E. M. et al. Seasonal human coronavirus antibodies are boosted upon SARS-CoV-2 infection but not associated with protection.
9. Tso, F. Y. et al. High prevalence of pre-existing serological cross-reactivity against SARS-CoV-2 in sub-Sahara Africa. Int. J. Infect. Dis. 102, 577–583 (2020).
10. BBC Discovery — Covid origins: The science