Vaccine-Induced Seropositivity (VISP)

What Is VISP?

Antibodies help prevent infection. Most vaccines stimulate the body to make antibodies. If you get a SARS-CoV-2 vaccine, your body will likely develop antibodies to the virus. Because of this, some antibody-based tests for SARS-CoV-2 infection (these test for antibodies) may return a positive result even if you are not, or were not previously, infected with SARS-CoV-2. This is called a vaccine-induced seropositivity (VISP) test result.
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Two Kinds of Tests Are Available for SARS-CoV-2

A viral test tells you if you have a current SARS-CoV-2 infection. This test detects the presence of the actual virus in your body. Some of these tests are referred to as PCR tests. A nasal swab or saliva sample is usually needed for this tes

An antibody test tells you if you had a previous infection. A sample of blood is needed to determine if your body has developed antibodies to SARS-CoV-2.

Right now, VISP shouldn’t be a problem because the antibody tests that are widely used do not detect the type of antibody produced by the current vaccines being developed. Instead, they pick up on a different antibody produced by a natural infection with SARS-CoV-2. However, this could change in the future as new antibody tests are developed.

Vaccine Antibodies vs. SARS-CoV-2 Infection Antibodies

Your body will make different antibodies in response to SARS-CoV-2 infection than in response to vaccination.

One of these antibodies is called a “spike antibody,” meaning that the antibody is directed at the spikes that surround the virus’s outer shell. The antibody attaches itself to the spikes on the virus in order to prevent the virus from attaching to your body’s healthy cells and causing infection. These are the types of antibodies that vaccines aim to teach your body to make in order to protect against infection.

Natural infection with SARS-CoV-2 will produce different antibodies. These antibodies can bind to not just the spike, but also to other viral proteins such as the nucleocapsid. Current vaccines in development do not lead to antibodies against the nucleocapsid protein.

Most antibody tests currently in use will only detect the second type of antibody that is produced by a natural infection with SARS-CoV-2. As time goes on and more vaccine candidates are tested, however, new antibody tests might be developed that also detect antibodies that binds to the virus’s spikes. If this happens, it means you could get a positive antibody test result, even if you have never been infected with SARS-CoV-2. Health care providers may not interpret your test results correctly as an immune response to a vaccine; they may incorrectly see it as an indication of prior infection with SARS-CoV-2. Once an effective vaccine is found and widely administered to the public, testing technology will need to clearly distinguish between vaccine responses and infection.