Antibodies and T- cells are produced in response to viral infections and immunizations, and they are specific to the protein sequences of each virus. The immune system “reads” those protein sequences during infections and immunizations and makes particular antibodies and T cells specific to them.
The immune system also retains the information in its memory. By doing so, if the same virus or its variants shows up again, the immune response is faster, and infections are stopped at their earliest stages.
Here is what an antibody looks like. Note that the yellow antigen binding site is specific to the yellow antigen.
And here is what a human T cell looks like under a scanning electron microscope
The Omicron Variant
The Omicron variant makes up 95% as of COVID-19 in the US. The Omicron is more transmissible but less deadly than the Delta variant.
Research that compared cases with Omicron and Delta variants was recently done in Ontario, Canada. There were more Omicron cases but fewer hospitalizations and deaths. Among 29,594 Omicron cases, 59 (0.51%) were hospitalized and 3 (0.03%) deaths. On the other hand, 11,622 patients with the Delta variant had 221 (1.6%) hospitalizations and 17 (0.12%) deaths.[1]
That is consistent with South Africa. A Higher number of COVID-19 cases but no change in death rates. The South African omicron experience
The higher transmissibility is because the Omicron variant can evade antibodies.
- Omicron can evade antibodies from vaccinated and COVID convalescent people
- Study shows the absence of omicron neutralization with the Pfizer and AstraZeneca shots
But why the lower deaths? What part of the immune system is giving protection?
Could it be the T cells? To find out serum from unvaccinated people who recovered from COVID-19 (unvaccinated convalescent) and those vaccinated with the Janssen-Johnson & Johnson COVID-19 vaccine (Ad26.CoV2.S), and Pfizer (BNT162b2) were tested against several antigens.
Antigens are proteins that elicit an immune response in the form of antibodies or T cells. There are different kinds of antigens within a virus, and they can vary from variant to variant.
For example, the SARS-CoV-2 will have antigens from the spike protein, the nucleocapsid, and membrane proteins.
This research used several antigens representing the following variants that dominated each wave inSouth Africa. The Wuhan-1 or the Ancestral variant started the pandemic, the Beta variant, the Delta variant, and the Omicron variant.
During those four waves, some unvaccinated people were hospitalized and recovered from COVID-19, and their blood was in storage. Their blood was used to study the T cells, representing the unvaccinated convalescent.
I previously mentioned blood from the people vaccinated with Pfizer BNT162b2 and Johnson & Johnson Ad26.CoV2.S were also analyzed.
Results
Briefly, the research showed that 70-80% of the T-cells from the vaccinated and the unvaccinated convalescents from previous infections with the Ancestral, Beta, and Delta variants were effective against the Omicron variant.
The magnitude of the T cells responses was similar to that of the Beta and the Delta variants and the T cell responses against the Ancestral spike, nucleocapsid, and membrane proteins. The authors conclude,
These results demonstrate that despite Omicron’s extensive mutations and reduced susceptibility to neutralizing antibodies, the
majority of T cell response, induced by vaccination or natural infection, crossrecognises the variant.Well-preserved T cell immunity to Omicron is likely to contribute to protection from severe COVID-19, supporting early clinical observations from South Africa.
A Higher number of COVID-19 cases but no change in death rates. The South African omicron experience
The study SARS-CoV-2 spike T cell responses induced upon vaccination or infection remain robust against Omicron, a preprint and available at medRxiv.
In summary, the people who recovered from COVID-19 infections and the ones who got the shots have protective T-cells against the Omicron variants that explain the mild disease it causes. This is consistent with another research that was discussed at
People who recovered from COVID-19 have effective T-cells against the omicron
The good news about an Omicron infection is that Omicron infections elicit neutralizing antibodies against other variants of concern.
It’s just like getting an immunization.
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