Thank you for your kind comment.

Here are my answers to your questions:

1. Based on the recent reports, it appears that a higher percentage of the delta variant infections occurred in vaccinated people, which could explain why most of the infections are mild or asymptomatic; since they are already mounted with antibodies against the virus/spike protein from the vaccinations.

As to why some healthy people may succumb to covid irrespective of age; I have found an article that explains 2 possible reasons:

(i) some people may have mutations in the gene that controls interferons (IFN). These mutations could cause the delay/inhibition of IFN release or the expression of faulty IFNs, and thus leads to a dysfunctional immune system.
(ii) some people seems to have antibodies that attacks the IFN. These antibodies are called autoantibodies. One study showed that a percentage of people who had developed severe pneumonia seems to have the autoantibodies.

And interestingly, these patients do not seem to present any health complications before getting infected with covid-19. In other words, they appeared healthy before they got covid.


2. So far, I have not come across any reports of people who remain asymptomatic despite having a dysfunctional immune system; since people who are asymptomatic throughout the infection usually are able to mount an appropriate immune response to clear off the virus infection before any health complications occur.

When the virus enters the body, they start to infect the cells and manipulate the cell’s system to replicate themselves. It is possible that the viruses spread to other organs without us realising as reports have shown that viruses were detected from the stool of asymptomatic patients. This means that the virus was spread silently from the respiratory tract to the gastrointestinal tract.

3. The viral load actually depends on the initial viral exposure and how fast the virus replicates in the body. Based on many studies, the viral load is usually highest in the first week after initial exposure to the virus. But the difference between those who had asymptomatic/mild symptoms and those who progressed to severe covid is that the immune response in the asymptomatic/mild group usually are able to clear the virus quickly and allow the body to restore homeostasis. Whereas those who progressed to severe covid had delayed or prolonged immune response which leads to hyper-inflammation.

As such, whether a person is vaccinated or unvaccinated does not determine the viral load. Rather, it determines only how fast the immune response clears the virus from the body.

Of course, these are all based on my understanding of the topic and I may be wrong. Nevertheless, I hope I have answered your questions. :)