Having a negative titer after a vaccine might disappoint some folks, as a vaccine should lead to immunity and a positive titer test.
“The Red Cross tests every blood donation for a variety of infections. All blood, platelet and plasma donations on or after June 15, 2020 will also be tested for COVID-19 antibodies.”COVID-19 Antibody Testing
Sometimes though, a negative titer doesn’t mean what you think it means…
Why Was My Titer Negative After My COVID-19 Vaccine?
Take COVID-19 titer testing, for example.
“Serologic tests for SARS-CoV-2 are antibody-based assays that measure an individual’s humoral immune response to SARS-CoV-2. Therefore, unlike nucleic acid amplification tests (NAATs, RT-PCRs), which detect viral RNA, serologic tests do not directly detect pathogens. A positive serology result may indicate either a current or past infection, and does not differentiate between the two.”COVID-19 Antibody Testing
These titer tests can indicate if you have had a recent or past COVID-19 infection detecting either IgG or IgM antibodies.
They might also help determine your response to COVID-19 vaccination, but only if the titer test is measuring the antibodies that your vaccine stimulated your body to make.
For example, the Pfizer and Moderna COVID-19 vaccines both get you to make antibodies against the SARS-CoV-2 spike protein, so you would expect to have IgM and IgG antibodies to that after you are fully vaccinated.
“Elecsys® Anti-SARS-CoV-2 is an immunoassay intended for the qualitative detection of antibodies to SARS-CoV-2 in human serum and plasma. The assay uses a recombinant protein representing the nucleocapsid (N) antigen for the determination of antibodies against SARS-CoV-2.”Immunoassay to qualitatively detect antibodies against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)
You won’t have SARS-CoV-2 nucleocapsid antibodies unless you have been infected though. And a nucleocapsid antibody test is one of the methods the American Red Cross uses to screen blood donations. So don’t be surprised if you have been fully vaccinated, donate blood, and have a negative titer test.
Also keep in mind that there is no general recommendation to have your titers tested after getting a COVID-19 vaccine. And that’s good, because none of these tests are actually FDA approved to be used to confirm immunity after you are vaccinated.
More on Vaccine Titer Testing
- How Long Does It Take for the COVID-19 Vaccines to Work?
- Answering Your Concerns About the COVID-19 Vaccine Development Process
- Where Are the COVID-19 Package Inserts?
- How Often Should You Do Vaccine Titer Testing?
- Why Was My Titer Negative After My Chicken Pox Vaccine?
- How Do You Know If You Have Measles Immunity?
- Did Your Rubella Titer Come Back Negative?
- Did Your Hepatitis B Antibody Test Come Back Negative?
- Titers for Vaccine vs Natural Immunity
- Vaccine Titer Testing
- CDC – Serology Testing for COVID-19 at CDC
- FDA – Antibody (Serology) Testing for COVID-19: Information for Patients and Consumers
- COVID-19 Antibody Testing
- COVID-19 Antibody Testing at the Red Cross
- Immunoassay to qualitatively detect antibodies against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)
- COVID-19 Vaccine and Blood Donor Eligibility Information
- COVID-19 Serology Testing Explained
- Detection of Nucleocapsid Antibody to SARS-CoV-2 is More Sensitive than Antibody to Spike Protein in COVID-19 Patients
- What defines an efficacious COVID-19 vaccine? A review of the challenges assessing the clinical efficacy of vaccines against SARS-CoV-2
- IAC – Ask the Experts about COVID-19 Vaccines