What You Need to Know About Vaccine-Induced Sero-Positivity (VISP)

A common concern in HIV vaccine research is vaccine-induced seropositivity, or simply VISP. So besides being a mouthful, what is VISP? And can it affect me?

When our bodies meet a foreign substance, like a virus, our immune systems make proteins called antibodies. HIV vaccines work to spark immune responses. They encourage your body to create antibodies that can block infections.

The problem is that standard HIV tests detect antibodies, not virus. Standard tests can’t tell the difference between vaccine antibodies and those from HIV infection. People who get HIV vaccines may test positive on standard tests. But, this does not mean they have HIV.. If an HIV test checks for antibodies to HIV, then the test has done exactly what it was supposed to do. It provided an accurate result. What may be false is the interpretation of the results. It may therefore be a “false diagnosis.” We call this Vaccine-Induced Seropositivity (VISP) or Vaccine-Induced Sero-Reactive (VISR).

VISP can last for a short time or for many years. A 2010 study found that about 40% of people who got an experimental HIV vaccine showed some form of VISP. For some other HIV vaccines in testing, the rate of VISP may be even higher.

The good news is there are tests that look for the HIV virus itself. These tests are not done regularly. They are more costly than antibody tests. But we use these tests on a regular basis when someone might have VISP. For study volunteers, we do these tests for free, both while someone is a volunteer and after, if they have VISP.

Nonetheless, VISP can have serious consequences for some people. For some people, proving a negative HIV test can be a challenge. This issue can affect buying insurance, getting a visa for travel, or joining the military. It can also create issues with health care providers, sexual partners, or employers. They might discriminate against someone based on their perceived HIV status.

We support volunteers with these issues when they occur. If you’re in a vaccine study or thinking about volunteering, know what VISP means for you.

If you’re thinking about volunteering: Think about how VISP might impact your future plans and your relationships. Talk with the recruiters and research staff about VISP and any concerns you might have.

If you’re a current volunteer: It’s important that you get HIV tests only at your study site. Your study site will know what kind of HIV test to give you and how to interpret the results. Testing only at your study site will also help to protect the integrity of the study.

If you’re a past volunteer and have VISP: You can continue to get the right kind of HIV testing at your study site. If that’s not possible, you can call the HIV Vaccine Trials Network’s VISP Testing Service at 1-800-327-2932. Let your healthcare provider know about your participation in an HIV vaccine study. They may not know about VISP, so you may have to educate them. Contact your study coordinator for help if you encounter any issues related to VISP.