The study, Comparison of the immunogenicity of BNT162b2 and CoronaVac COVID-19 vaccines in Hong Kong, was published in the peer-reviewed journal Respirology.
The two injections are different. The Pfizer BNT162b2 uses the modified RNA technology enclosed in a lipid nanoparticle. In contrast, the Coronavac uses an old vaccine technology using inactivated viruses that cannot replicate and cause an infection.
The results show that one month after the second dose of vaccine, the Pfizer BNT162b2 elicited significantly higher measures of antibody effectiveness than Coronavac as measured by,
- Plaque Reduction Neutralization – quantifies the titer of neutralizing antibodies for a virus.
- Surrogate Virus Neutralization Test – detects antibodies without the need for a live virus.
- Spike receptor binding – antibodies to the spike protein
- Spike N-terminal domain binding – antibodies to the N-terminal domain of the spike protein (The spike protein has subparts. As shown below)
- Spike S2 domain binding – antibodies to the S2 domain
- Spike FcR binding is how well the Fc part of the antibodies binds to the immune cells to attract another immune cell once the Fab sticks to a virus.
- Antibody avidity levels – how well the antibodies bind to the virus
The other conclusion is that the Coronavac elicited more CD4+ and CD8+ T-cell responses to the SARS-CoV-2.
For background, below is an electron microscope of the SARS-CoV-2 spike protein. It is divided into the S1 in pink, S2 in cyan and orange, and the N-terminal domain in blue. The immune system makes specific antibodies for each subpart of the spike protein, and they were measured by 3,4, and 5 above.
Below is the representation of an antibody. The Fab part binds to the virus or bacteria, and the Fc part binds to an immune cell.
When the Fab of the antibody binds to the virus, the Fc part of the antibody sticks out. The Fc attracts an immune cell with an Fc receptor to phagocytose (eat) or destroy the virus-antibody complex. See the diagram below.
With that background, let me tell you what else is in the paper that was not mentioned in the abstract, which most people read.
The authors also took blood samples from people who recovered from COVID-19 as a control group and compared it with the Pfizer and Coronavac group.
The graphs below show that the (A) FcγRIIIa-binding S antibodies of the COVID-19 recovered are the same levels as the Pfizer and Coronavac. At the same time, the FcγRIIIa-binding N antibodies of the recovered COVID-19 patients are better than Pfizer and Coronavac (B).
FcγRIIIa, also known as CD16, are molecules found on the surface of natural killer cells, macrophages, and specific T cells. They serve as a marker on what the immune cells should attack. This system assures that only foreign substances are attacked by the immune cells and not the host. 
Source: Mok et al., 2021The avidity indexes of the recovered COVID-19 patients’ S FcγRIIIa (C), antibodies to the spike protein – S IgG (D), and antibodies to the nucleocapsid protein N FcγRIIIa (E) are also the same if not better compared to Pfizer and Coronavac.
Source: Mok et al., 2021The figure below shows the spike proteins protruding from the nucleocapsid in the center of the SARS-CoV-2.
The CD4+ and CD8+ T cells secrete interferon in response to viral infections. Interferons are signaling proteins that coordinate with the other immune cells so that the immune response will be orderly. Compare the interferon levels of the Pfizer, Covornavac, and COVID recovered below. The horizontal bars in the middle of the upright COVID-19 rectangle are the mean values.
The graph below presents the almost equal proportion of IFNγ producing interleukin-2 (IL-2) and tumor necrosis factor-alpha (TNF-α) CD4+ and CD8+ T cells from Pfizer, Coronavac and COVID recovered.
Interleukin-2 stimulates the production of more T-cells, and tumor necrosis factor-alpha is a mediator of inflammation. Both IL-2 and TNF-α are essential to fight infections.
Source: Mok et al., 2021Lastly, the graph below shows the Interferon-gamma (IFNγ) responses for T effector memory (TEM), central memory (TCM), terminal effector memory (TeEM), or naïve (TN) CD4+ and CD8+ T cells post-vaccination.
There is not much difference between Pfizer, Coronavac, and people who recovered from COVID-19.
I don’t know why the study did not include the results about the COVID-19 patients in their abstract, and it could be because it is not the study’s objective.
Take Away Message
Based on this study, Pfizer and Coronavac shots elicit the same immune response as the COVID-19 convalescent people, although vaccine-induced antibodies from both decline significantly after six months.
Durable Immunity from Pfizer COVID-19 Vaccine Lasts only Six Months.
This study also shows that natural immunity against COVID-19 is about the same compared to the vaccines. However, in other studies, natural immunity against SARS-CoV-2 is more robust and durable.
- Naturally acquired antibodies from COVID-19 last up to 20 months
- T cells from prior coronavirus protect, and nucleocapsid directed COVID-19 shots may work better
- T cells from previous infections and shots are protective against the Omicron variant
- Omicron infections elicit neutralizing antibodies against variants of concern
- High Anti-SARS-CoV-2 Antibodies Among the Unvaccinated in Bangui, Central African Republic
- COVID Vaccines are Non-Sterilizing and Can Lead to More Infectious Variants
- Study Shows Decreased Antibody Response to Breakthrough Infections
- Pre-Existing T-Cells Stop COVID-19 Before it Starts
- Breakthrough Cases Spread COVID-19 as Easily as the Unvaccinated
- Harvard: Immunity from mild COVID-19 infection much better than vaccination
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Reference:
, , , , , , et al. Comparison of the immunogenicity of BNT162b2 and CoronaVac COVID-19 vaccines in Hong Kong. Respirology. 2021; 1– 10. https://doi.org/10.1111/resp.14191
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