Mechanism of Covid vaccines

  • #1
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Summary:
What is the mechanism/physiology in which the covid vaccines help smothering the disease progression and hospitalization?
As the covid vaccines become more prevalent worldwide, the hospitalization and mortality rates are coming down hearteningly.

Actually, what happens after vaccination?

1) Vaccination causes the production of antibodies. So when later infection happens, the antibodies are up and ready to bind and neutralize the viruses.
2) Is antibody production, the only mechanism that prevents disease progression?

What about the other components of the immune system? How do they react, after vaccinated people are infected by SARS-CoV2? Do the following get suppressed or do they get activated in breakthrough infections?

i) The complement activation?
ii) The other cytokines?
iii) The platelet activation?

Apart from these, how do the following immune components behave after vaccination?

iv) Innate immune system reaction?
v) T-cell reactions - CD8+ and CD4+
vi) Whether th1 pathway dominates or th2 pathway dominates?

Overall, how do we compare the exact mechanisms of the total immune reactions of vaccinated and unvaccinated people?

In other words, exactly what is the mechanism/physiology in which the vaccines help smothering the disease progression and hospitalization?

Thank you,
 
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Answers and Replies

  • #2
Ygggdrasil
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Here's a passage from an article on adaptive immunity to SARS-CoV-2 that has a decently good explanation:
An ideal COVID-19 vaccine would elicit long-lasting high titer neutralizing antibody titers and would provide sterilizing immunity to prevent disease and onward transmission. Even if that is not accomplished, a vaccine could still be highly effective at preventing serious COVID-19 disease. If the neutralizing antibody titers are sufficient to blunt the size of the viral inoculum, the presence of memory T cells may control the infection. The working model described above (Figure 2), with severe COVID-19 cases being associated with a failure to make a T cell response fast enough during natural infection with SARS-CoV-2, is good news for vaccines, because vaccines overcome/bypass the speed problem of adaptive immunity and T cell responses. Priming of the immune system by a vaccine happens well in advance of virus exposure. Additionally, the findings that Spike is a good target for CD4+ T cell responses, Tfh cell responses, and CD8+ T cell responses in SARS-CoV-2-infected people is good news for vaccine development (Grifoni et al., 2020; Juno et al., 2020; Rydyznski Moderbacher et al., 2020; Peng et al., 2020), because almost all COVID-19 vaccines target Spike only.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7803150/ (The full article is a great reference on the immunology of SARS-CoV-2 and very much worth a read)

In other words, vaccines will primarily protect from infection through the production of neutralizing antibodies that can bind to an inactivate the SARS-CoV-2 virus. If these antibodies are not present in high enough amounts (due to waning immunity over time) or are not as effective (due to the emergence of new variants), T-cells can protect against severe disease by helping to control the infection by culling infected cells and stimulating memory B cells to make antibodies again.

Consistent with this model, new research examining the correlates of protection for SARS-CoV-2 suggests that the amounts of neutralizing antibodies correlate well with protection against infection. Note that this research does not necessarily suggest that neutralizing antibodies are the only source of protection; production of an antibody response depends on an efficient CD4+ T-cell response, so the presence of neutralizing antibodies reflects both a functioning antibody response and a functioning T-cell response. Experiments in animals suggest that both the antibody response and the T-cell response help protect against infection.
 
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  • #3
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Thanks Ygggdrasil

That was a wonderful link you have provided. It discusses a lot more covid information scientifically. It is a treasure of information.
 

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