Survey of the Health of Wisconsin and the Past Antibody COVID-19 community survey logos.

PACCS Frequently Asked Questions and Resources

The SHOW Past Antibody COVID-19 Community Survey, or PACCS, is starting its third and final wave of testing this spring. With COVID-19 vaccines becoming available, we would like to offer additional resources on:

  • How antibodies work
  • How the COVID-19 vaccine and other vaccines work
  • What our antibody test looks for

Our scientists prepared a chart to compare the different antibodies made when you receive a vaccine and when you are infected with the COVID-19 virus.

Download it here:

Vaccines and COVID-19: the body’s response

PACCS Frequently Asked Questions

I have received one or two doses of a COVID-19 vaccine already. Can I still participate?


Will the vaccine affect my antibody test results?

No. This antibody test will only be positive if you were infected with the COVID-19 virus. It will not be positive if you were vaccinated but never infected. This test measures a different antibody that your body makes only after you are infected. It is different than the antibody your body makes after you are vaccinated with the recent vaccines.

If I have had the vaccine and my antibody test results are negative, does that mean the vaccine did not work?

No. Your antibody test will only be positive if you were infected with COVID-19 virus and not if you were vaccinated. This is because the antibody test we use measures N-protein antibodies, produced only after infection. The vaccinations were made so your body makes S-protein antibodies. The antibody test we use doesn’t measure S-protein antibodies.

What are antibodies and immunity?

Antibodies are made by your immune system to help you fight off viruses and infections. It can take weeks to months for your body to create antibodies. There are many different types of antibodies that exist.

The antibody test used by the Wisconsin State Laboratory of Hygiene is an IgG test. The IgGs are antibodies that are made 2-3 weeks after infection and are expected to last several months or longer.