What You Need to Know About VISP (Vaccine–Induced Sero–Positivity)
One of the most common concerns people have about HIV vaccine research is around vaccine–induced Seropositivity, or VISP. So besides being a mouthful, what is VISP? And can it affect me?
When our bodies encounter a foreign substance, like a virus, our immune systems produce proteins called antibodies. HIV vaccines are designed to provoke immune responses —this includes causing your body to make antibodies, which can prevent infections.
The problem is that standard HIV tests detect antibodies, not virus. Common tests do not differentiate between antibodies that are the result of a vaccine and antibodies that are the result of HIV infection. Study participants who receive HIV vaccines will often test positive (seropositive) on these standard tests but it doesn’t mean they are HIV-infected. If an HIV test is designed to look for antibodies to HIV, then the test has done exactly what it was supposed to, and got an accurate result. What may be false is the interpretation of the results. It may therefore be a “false diagnosis.” We refer to this as Vaccine –Induced Seropositivity (VISP) or Vaccine –Induced Sero –Reactive (VISR).
VISP can last for a short time or for many years. A study from 2010 actually found that around 40% of people who had received an experimental HIV vaccine developed some sort 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 routinely done because they are more expensive than tests that just look for antibodies. But we use these tests routinely 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. It may present problems for people who are asked to provide proof of a negative HIV test to buy insurance, get a visa to travel, or join the military. It may also cause problems with health care providers, sexual partners, employers, or others who may discriminate against someone because of their perceived HIV status.
We help volunteers deal with these kinds of issues when they come up, but if you’re in a vaccine study or thinking about volunteering, it’s important to consider what VISP might mean 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.