In Canada (and elsewhere including US and UK) Roche provides a panel of two serum antibody tests. First developed was the N test to identify antibodies against the Nucleocapsid protein. This test will accurately detect responses to natural infection, but not an immune response triggered by a vaccine.
The S test seeks antibodies against the S (Spike) proteins. The Elecsys® Anti-SARS-CoV-2 assay characteristics are described at Roche diagnostic website. Excerpts in italics with my bolds.
A positive result means that you have developed protective IgG antibodies to the spike protein of the SARS-CoV-2 virus. Our report will also provide you with a numeric count of these antibodies which is standardised and allows you to compare with other available tests and published WHO standards.
This test will detect antibodies amongst individuals who have been naturally infected but also received one of the following vaccines: AstraZeneca, Pfizer / BioNtech, Moderna.
If antibodies are detected, it means that the immune system will recognise the SARS-CoV-2 virus if met in the future and this will prevent serious reinfections from occurring. There is no way of predicting the level of that protection.
A negative result tells you that you likely have not been exposed to SARS-CoV-2 or that the level of protective antibodies have subsequently decreased to a point where they can no longer be detected.
How Immunity Deploys Antibodies
Testingforall in UK provides this helpful information Understanding your Roche Anti-SARS-CoV-2 (S) test result
The body has a range of ways to fight off infection, but the scientific community has centred the development of vaccines for COVID on triggering the creation of antibodies to the spike protein of coronavirus. These “spikes” are what gives coronaviruses their name, and it is through this spike mechanism that the virus binds to healthy human cells in order to replicate itself.
A natural infection creates a wide ranged defence, often involving a T cell response to destroy human cells infected by SARS-SoV-2 to stop virus from replicating, and by the creation of a range of antibodies to different proteins in the virus that attempt to deactivate it before it can bind to host cells. The original COVID-19 Home Total Antibody Test we launched in Sept 2020 detects antibodies to the Nucleocapsid protein that surrounds the RNA of the coronavirus, and is useful for detecting previous exposure, which has provided many people with an understanding of whether past or ongoing symptoms that they experienced were related to a coronavirus infection that occurred before PCR testing was widely available.
The COVID-19 Immunity Test provides an accurate calibrated measurement of the level of antibodies to the spike protein, and is therefore considered to be a good view of your immune response and status. In the testing that we have carried out with our laboratory partner, we have compared the result of the both the Roche N and S test tests on positive blood samples and see very good agreement so if you tested positive on our COVID-19 Home Total Antibody Test then you will very likely test positive on the COVID-19 Immunity Test. The difference between the two tests is that they are looking at different viral protein targets, and that the Immunity Test gives you a calibrated antibody titer that can be compared to other tests and the emerging WHO standard.
The Results in My Case
My N test was negative while my S test was highly positive at >2500 U/ml. Here is the range of reported results:
|Result Type||Level (U/mL)|
Antibodies not found
|< 0.4 (less than 0.4)|
|Between 0.4 and 0.8|
|Between 0.8 and 10|
|Between 10 and 100|
|Between 100 and 250|
|Between 250 and 1,000|
|Between 1,000 and 2,500|
|> 2,500 (more than 2,500)|
Conclusion: My Pfizer jab #1 was in April, #2 in June. Six months later I have the highest rating for antibodies against the Spike protein, a combination of natural and vaccine-induced immunity.
Footnote: For a review of all the ways Ivermectin defeats SARS CV2, see How Much Does Ivermectin Fight Covid19? The Count is 20 ways.
I noted that 2500 units per milliliter is the same number as the air molecules (mostly N2 andO2) surrounding each CO2 molecule in the atmosphere. The analogy is clear: Just as IR-inactive gases keep our planet warm without overheating, our immunity antibodies keep us from Covid19 fever.