"Infectious viral load (VL)"
https://pubmed.ncbi.nlm.nih.gov/35395151/
"the antigen to which the immune system responds is a relatively small number of amino acids or peptide."
https://www.who.int/teams/health-product-policy-and-standards/standards-and-specifications/vaccine-standardization/synthetic-peptide-vaccines
"Peptide antigen, namely, a peptide used to trigger animal's immune system to develop antibodies specific to that peptide. Nowadays, the use of synthetic peptide antigens as immunogens has markedly increased, and this technique is also widely applied for immune research"
https://www.creative-peptides.com/services/peptide-antigen-design.html
"The spike protein is found on the surface of the virus that causes COVID-19. After the protein piece is made, our cells break down the mRNA and remove it, leaving the body as waste.
Next, our cells display the spike protein piece on their surface. Our immune system recognizes that the protein does not belong there. This triggers our immune system to produce antibodies and activate other immune cells to fight off what it thinks is an infection. This is what your body might do if you got sick with COVID-19."
https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/mrna.html
"Currently authorized SARS-CoV-2 antibody tests have not been evaluated to assess the level of protection provided by an immune response to COVID-19 vaccination. If antibody test results are interpreted incorrectly, there is a potential risk that people may take fewer precautions against SARS-CoV-2 exposure. Taking fewer steps to protect against SARS-CoV-2 can increase their risk of SARS-CoV-2 infection and may result in the increased spread of SARS-CoV-2."
https://www.fda.gov/medical-devices/safety-communications/antibody-testing-not-currently-recommended-assess-immunity-after-covid-19-vaccination-fda-safety