Infections
Varicella Zoster antilichamen
Antibodies against the chickenpox virus; show whether you are protected, especially important when planning a pregnancy or during pregnancy.
Everything about this testWhat it measures
The varicella zoster virus (VZV) causes chickenpox and sometimes, later, shingles. After chickenpox or a vaccination, the immune system makes IgG antibodies (defense proteins) against the virus, which usually remain detectable for life. The test measures the amount of VZV IgG in the blood. Above the cut-off value of the test (100 or 150 IU/l, depending on the test), someone is considered protected against chickenpox.
- Protection against chickenpox after a past infection or vaccination
- No detectable protection: a chance of chickenpox, with extra risks during a pregnancy
Positive
A positive result means that antibodies have been found: you have had chickenpox or have been vaccinated against it. According to the Dutch medical specialists' guideline (FMS) on varicella, you are then considered protected against chickenpox; chickenpox despite a positive result is rare. A pregnant woman with a positive result does not need to take extra measures after contact with someone with chickenpox or shingles. The result says nothing about the chance of shingles later, because shingles develops when your own virus, already present in the body, becomes active again.
Negative
A negative result means that no or too few antibodies have been found; you may then still be able to get chickenpox. Because about 95 in 100 people in the Netherlands have antibodies, this is not common in adults, and the usual tests sometimes miss low amounts of antibodies: according to the FMS guideline, with a negative result there is a real chance that there is protection after all. A negative result is more common in people who grew up in a country where chickenpox is less common. During a pregnancy, chickenpox can be severe: about 5 in 100 pregnant women with chickenpox get pneumonia, and with an infection between weeks 13 and 20, about 2 in 100 children have a congenital abnormality.
If your result is abnormal
With no antibodies and a wish to become pregnant, the GP can discuss vaccination against chickenpox; after the vaccination, the advice is not to become pregnant for 4 weeks. If a pregnant woman without detectable antibodies has had contact with someone with chickenpox or shingles, she can receive antibodies (immunoglobulin) within 10 days via the midwife, GP or hospital. Individual cases of chickenpox are not notifiable.
Reliability
According to the Dutch medical specialists' guideline (FMS) on varicella, someone with detectable VZV IgG is considered protected and someone without detectable IgG is considered not protected. The tests widely used in the Netherlands are very specific (more than 98 percent), but miss some low antibody levels: a positive result therefore predicts protection very well, a negative result much less so. Your medical history is also reliable: anyone who knows for sure they have had chickenpox is almost always protected, while 43 to 75 percent of adults who think they have never had it do have antibodies. According to the LCI guideline (RIVM), IgM is not very reliable for showing a current infection.
Limitations
- The cut-off value differs per test (100 or 150 IU/l); a result just below the cut-off value can still fit protection.
- After vaccination, the amount of antibodies can be lower than after having had chickenpox and sometimes falls below the cut-off value.
- After a blood transfusion or administration of immunoglobulins, antibodies from donors can temporarily be measured as well.
- With a weakened immune system, the amount of antibodies says less about protection.
How common is this
In the Netherlands, about 95 in 100 people between 0 and 79 years of age have antibodies against the chickenpox virus; among 6-year-olds this is already more than 95 in 100. In 2022, GPs registered about 4 in 1000 people with chickenpox, mainly young children. Vaccination against chickenpox is not part of the National Immunization Program in the European Netherlands.
Who is this useful for
Useful for women who are planning a pregnancy or are pregnant and do not know for sure whether they have had chickenpox; the Dutch medical specialists' guideline (FMS) on varicella recommends discussing the test if your history is negative or uncertain. Also useful for people who work with children or vulnerable patients and have not definitely had chickenpox or grew up outside Western Europe, and before a treatment that strongly suppresses the immune system. Anyone who knows for sure they have had chickenpox, or in whose family a child had chickenpox, usually does not need the test.
Downsides and risks
- A negative result in someone who is in fact protected, for example after vaccination or with antibodies just below the cut-off value, can cause unnecessary worry or an unnecessary vaccination.
- A negative result during pregnancy can cause concern, while vaccination is then no longer possible.
Sources
- LCI-richtlijn Waterpokken (RIVM, 2024)
- FMS Richtlijnendatabase: Varicella, module Bepaling VZV-serostatus
- FMS Richtlijnendatabase: Varicella, module Seropositiviteit als maat voor bescherming
- Thuisarts.nl: Ik ben zwanger en ben in de buurt geweest van iemand met waterpokken of gordelroos
- NHG-Standaard Preconceptiezorg (M97)
Always discuss an abnormal result with your GP. If a result is strongly abnormal, we try to reach you as soon as possible. Read your result yourself as well and contact your GP if in doubt. A test does not make a diagnosis. Read more about risks and results